Ok I am new and I take pictures with an older nikon coolpix camera, I usually just edit with snapseed free app on my tablet then if I wanna change it a little more use an Instagram filter. My subjects are usually motorcycles and barns things like that so objects. I've been asked to sell digital copies online so will need to watermark and lower the resolution for online viewing. Which program is best and which is cheapest. Thanks!
For your level of work, neither Photoshop or Lightroom is needed. Just get an account with an online photo gallery/selling site and they should automatically be able to generate lower quality previews and watermark them for you. You don't need software like Lightroom or Photoshop to do that kind of very basic work.
If you really want to do it yourself. GIMP will also easily let you do it and is free.
Also, do keep in mind what others have mentioned. Image theft isn't really going to detract from your sales as long as people understand that you reserve rights on your images. Those who want to use them or get nice prints of them will buy them regardless as long as you aren't asking anything outrageous for them and those who are going to take them won't be dissuaded by low quality and watermarks (though potential customers might be).
Also, don't be surprised if simply posting your images online doesn't generate any sales. Sales is hard. It generally involves grunt work on the ground promoting your images. The site is just an easy place to tell people to go to buy a copy if they want one. You most likely won't get many "walk ins" if any.
Setting up a random website no the web is kind of like opening a store in the middle of a deserted ally. Without driving people to it, nobody will ever even know it is there. Going with one of the bigger sites that does image sales does help some, since people can like your images and cause them to get more attention, but it's still pretty much a luck game more than skill unless you are actively promoting your work.
If it is something you really want to try to get in to, it might also be worth pursuing some better camera equipment and better software for touching up the photos to make a more professional level product. There's a lot you can't do with a cheap point and shoot and basic instagram filters that can be improved on a lot with better software. If you really want to get involved in photography, try picking up and learning a basic DSLR, shoot RAW and try learning something like GIMP or Darktable to learn about photo adjustments and digital darkrooming. It will probably help improve your end result.
I am sure that you are a talented photographer, and your images are fantastic. Even so, you will find few such talented people who manage to sell even a single, fabulous photograph. This not because someone can steal them online, but mostly because anyone can get nearly any image they want via vary inexpensive stock photography sites.
I have seen photographers spend huge amounts of time managing and editing images to keep those online from stealing or 'taking money from their pockets'. You should also know that someone who really wants to take your online image, will do so, regardless of watermarks or resolution. It will shock you what people are happy with to use as an image online. Often they even attempt to crop your image to remove the watermark. This may strike you as illegal, and it is. However, rarely is this done for commercial purposes, and most often I find the individual doing it would never, ever, consider purchasing an image...its not worth the money to them. In other words, they never were a customer, so there is no 'lost sale' or money taken from your pocket: they never would have bought in the first place. If you are not willing to take legal action against every infringement, perhaps you need to spend your time on other parts of your photography business.
Those that truly want to purchase your photo will contact you to do so, whether you post the full original version or not. Those with money for photos are concerned about legal implications around using photos, and have budget to purchase photos. In other words: don't worry about resolution.
As for watermarks, its best to consider them as marketing expense, not theft protection. Make your watermark unobtrusive, but useful, so that when used for placement or displayed for client consideration, your beautiful image is preserved, but its clear to whom the images belong.
I recommend Lightroom to do this, as Lightroom is simply a must have software for any photographer (IMHO) and makes it easy to add watermarks when you export the images. Or, many may suggest Photoshop to do this. If you go that route, I suggest the book "PS5 Photoshop for Photographers", which provides step by step instructions for watermarking and lots of other things. If you don't have or want Lightroom or Photoshop, then I recommend Acorn for the Mac, which is a nice tool that supports layers (Check out this instruction http://flyingmeat.com/acorn/docs/batch%20watermarking.html). Sorry I don't know much about Windows apps for this.
Of course, when you take a photo, you automatically have Copyright for that work. However, to really get anywhere legally, you must register those images with the Copyright Office (USA). This is really as simple as mailing the images to the Copyright Office. But, there is an alternative called Creative Commons, that is a way of declaring how you want your images used, and that you will work with others on this use. So instead of worrying about all usages of your image, Creative Commons lets you indicate your desires such as: that 'its ok to use the image if its non-commercial, but at least give my name and website when you do'. Think of this as simply a more pragmatic 'copyright'.
The easiest way to do this, I think, is to post your images on Flickr,who offers great tools to tag images as Creative Commons. Flickr has very good information at http://www.flickr.com/creativecommons/ and http://www.flickr.com/account/prefs/license/ Perhaps you start with Noncommerical + No Derivative Works.
Regardless of all, that has been said about watermarks, I always add URL of my website, so when someone shares my photo, it's easy to find the source.
I use Picasa for that. It's free software. Select photos you want to publish, then go to File > Export photos to folder... (or press Ctrl + Shift + S). Here in one step you can resize photo and add text as watermark at the bottom.
Lightroom also can do this. When you go to Export, you can define your watermark and save it as template. Watermark can be text (eg. your name or website) or image (logo or stylized text).
basically, watermarks won't stop anyone. At best, they are a reminder that the image isn't public domain, and a way to help prove willful copyright violation when the person crops the watermark off and uses the image anyway. It's counter productive to damage an image to make it uninteresting to copy because it usually makes it uninteresting to look at.
Two expert opinions on this that I trust have very interesting and well thought out views:
Duncan Davidson: http://jdd.io/post/64659529445
if you're brand new to photography, don't worry about it, worry about getting better and enjoying taking pictures. There'll be a point in your career where this might matter, but you're better off worrying about becoming a better photographer than avoiding some incidental copying.
Why don't you try Mass Watermark http://www.masswatermark.com .It can bulk watermark,resize,add exif and direct export to picasa/Flickr.Its not free though costs $30.I have been using it for a while,no problems
If you want several files watermarked at once, or a folder full of files, you can use my watermarking program SquiggleMark. (Disclaimer: I am the author of SquiggleMark)
It is free to use.
You can position your watermark, resize it, set its transparency, and watermark a bunch of files all at once. Works on Windows, Mac and Ubuntu.