Don has a point, if you are wondering about the very basics asking if a fairly quirky five year old camera would be a good choice you are starting off in the wrong end. By all means the 50D is a competent camera but hardly my first choice. I’m guessing from your suggested body your budget is pretty tight. If that is the case I’d look at either a canon 5D (the original 12mpix version), Canon 7D (original 18mpix version), canon 1Ds MkII, Canon 1D MkIII, Canon 70D or 6D. Out of that lot a used 6D would be my choice but most expensive. All the listed cameras will be competent enough if you know what you are doing and several a couple of generations old pro-bodies and they are listed roughly by ascending price on the used market. As for Nikon I don’t know to be honest as I don’t know them so well. The Nikon D300s is always a favourite as is the D7100. Nikons D600 will win on price/performance ratio as they have cannonballed in value after the scandals with dirty sensors and a replacement coming out.
Lens will get a lot more difficult as that will depend on the body but if you get a full frame camera a 24-70 f2.8 lens would be the obvious choice. Combine with canons excellent 85mm 1.8 or 135mm f2 and you have a solid package. After that you should think about spending twice as much as you did on body and lens to get a good light set up.
If you were looking for encouragement to start up a facebook photography business without any experience you have landed in the wrong forum I’m afraid.