If all you own is a crop-body d-slr and a 50.1.8 lens, you are exceptionally under-capitalized and honestly, your work could not help but reflect that. It's difficult to hear at times, but the difference to me between a professional photographer and a wanna-be or part-timer is in both results, but also capability and familiarity with a suite of tools. In this thread we've talked about mechanics, but the idea of a mechanic with only ONE single wrench is as absurd as the photographer with a crop-frame body and nothing more than a 50mm lens...that's simply not enough equipment to offer first-class photography. It's just not. Just as one, single wrench is not enough to be a mechanic.
Professional photographers that cannot afford even the basic equipment that 95% of professional photographers own...hmmm...no wide-angle photos? No telephoto images? No flash? No reflectors? I dunno...sounds very low-rent to me. Sounds a lot like the "professional carpenter" (self-professed) who cannot afford anything except a nail gun...no square, no level, no circular saw, no nothing....except the ability to air-sink nails with a nailgun. "Nailgunner" is my personal terms for a number of modern day "carpenters" who cannot even handle an actual hammer...these are the $15/hr. guys hired to do framing work on spec houses.
If the OP wants to come back and flesh out his or her inquiry with a bit more detail, that might be helpful, but the OP itself mentions nothing but a crop-body camera and a 50mm lens and the inability to afford even a third-party 70-200...like a mechanic with one wrench, or a carpenter with ONLY the ability to nail gun in nails...