50K will take a while to get to. You're basically starting at the bottom of an industry where entry-level regional pilots are making in the 20k range. For some stupid reason, flight instructing is often viewed as even lower on the pole than regional pilots. I'm doing ok as a flight instructor, but nowhere near making 50k and I'm working my ass off. Take a look at the pay rates on this site. Starting is around $20 per hour for most regionals. However, you cannot assume that you'll be working 40 hours per week. This pay is usually "block time" or something similiar. You're only making that wage when the aircraft's engines are running. Yeah, there is perdiem but you're realistically going to bill 70-100 hours a month at that rate that's listed.

There is no reason why you can't do both ratings if you have the time to commit to it. I have friends that went from 0 time to CFI at a local FBO in that amount of time. One of my fellow instructors did his commerical and CFI in less than a month (he was building cross country time for about 6 months prior to this).