Michael, you shouldn't be purchasing any equipment, wetsuit or BCD, until you have at least found out if you can dive or like diving. After you get in the water, there may be a physical problem that prevents you from not only just diving, but being comfortable diving---who takes up a sport that makes them miserable? I'm a big guy too and have also outfitted my teenage grandaughter, there are similar problems. She is small but is growing, you are large and shrinking. Buying a wetsuit that you have to replace every six months is expensive, as is buying a BCD that won't fit or requires extensive refitting. At least use rental gear for the first couple of pool sessions to determine if you want/can do this. I know of several students who never came back after their first time underwater---just in the pool, for physical and personal reasons.
My experience with recreational BCDs was negative, I went through three in the first year I was diving----expensive. I read about backplate/wings and found a dive shop familiar with them and they helped me get set up----I'll never go back. They are easily and cheaply re-sizable and you have options with them BCDs don't offer.
Critical to your situation is going to be weight distribution and the amount of weight you will have to carry, given your size and the amount of neoprene you will have to wear to stay warm. I currently use a 9 pound backplate with a 6 pound single tank adapter, this coupled with my steel tank only requires ten pounds of ditachable weight on my weight integrated BP belt. Having just converted to a drysuit, I'm now looking at transferring my harness to a 12 or 15 pound backplate as I had to bump up my wieght a little for the drysuit. I have also successfully used two 9 pound backplates bolted together in the past when I had a two piece wetsuit that was very bouyant.
My daughter is a big girl, her instructor had her certify with a BCD and a 40 pound weight belt doing shore dives---she was miserable. I built her a BP wing and she uses the same configuration I do and she now loves diving. There are several weight pouch designs that fit on BP wing belts, being round like we are---you will hate a weight belt. Also consider mounting weight in pouches on the top strap of your tank to help balance your load, this can also be done with a BCD and fairly cheaply.
My grandaughter was too small for rental suits---they fit, but badly. We finally bought her a Henderson hyperstretch and it stretches enough that it still fits her 1.5 years later. She also dives a BP wing but uses no weighted single tank adapter, and six pounds on ditchable weight in her pockets, along with a steel tank. Steel tanks can also help with your weighting situation as they aren't bouyant.
You would really feel bad if you made substantial investments in equipment only to find out you don't like diving. By the way, I'm an avid underwater photographer, if you think scuba gear is expensive wait till you look into the underwater photography stuff. Sorry this got so long---but LDS' sometimes don't do the right thing.
