Most professional setups start with a 24-70/2.8 and 70-200/2.8 two-lens combo on full frame and work outwards from there. These are the two general-purpose bread'and'butter lenses for a lot of pros simply because they're versatile being both fast (f/2.8) and zooms in the most common focal length ranges. Whether or not they'll be ideal for you, however, is not something we can answer. Lens choices are individual and a lot of factors such as what/how you plan to shoot and your personal budget are also huge determining factors that only you really know. People can tell you what works for them very easily. Telling you what will work for you is less easily arrived at.
It's super-easy to tank a photography business with gear greed. A 24-70/70-200 f/2.8 combo is expensive (upwards of $2500) as is a full-frame body. If you have to make your business go into the red to purchase these lenses, it's probably a very bad idea. Because we all know a lens alone isn't enough to guarantee an image. In addition, the 24-70 is designed for full frame. On a crop body, a 17-50ish/2.8 lens is FoV equivalent to what a 24-70/2.8 does on full frame.
But maybe you only need an 85/1.8. Or specialized software. Or a flash. Or off-camera flash gear and knowledge. Before buying something, you should know whether or not you need it, and it doesn't sound like you do. What is your 50mm not doing that you need to do? Start there.
Renting can be a good way to use only a small amount of money to try a lens before sinking money into purchasing it. Until you gain a wide degree of experience with lenses, it's tough to know what you want, and renting is one way to experience a lens with enough time to learn its ins and outs.