I agree with lucienrau that larger bikes are hard to find on craigslist. FYI - I rode a giant cypress dx across Kansas in the annual bike across Kansas. I was at 365 lbs and 6'3". Year one i broke 5 spokes, year 2 had flat tire issues. I will give the Giant credit, the bike was approx 6 years old and figured broken spokes would eventually occur. I had to buy a new back rim in Hutchinson, Kansas. Less quality rim but more spokes and it solved the problem.
The cypress model has front shocks but they will lock out. Someone will always say to avoid shocks if you are a clyde. I agree. Front shocks are scary at 350 plus lbs.
I will eventually buy a road bike but for now just ride my current bike and try to lose weight prior to this years Bike Across Kansas in June.
Remember, this will not be the last bike you buy. I hope you lose weight and ride the hell out of whatever bike you buy and are forced to purchase another.