I don't have any specific advice but I wish you all the luck in the world. I think maybe a rigid mountain bike would be a good choice. If you have the money you could probably buy a set of heavy duty wheels that would last a long time. Keep us posted on your progress. A young woman that works for me went from 270 to 125. I'm trying to get her on my "Tour De Cure" team but she still won't wear spandex. Where you live you could probably bike most of the year and do some weight training when you can't. I'm sure you will do well.