Atomic
What a great attitude you clearly have regarding your health and cancer. And attitude definitely affects your health. So you're golden!
I suggest starting with something used. Ebay perhaps? I am upgrading only 1 year after buying my bike, and I know lots of others have too. It would have been a lot smarter to buy what I thought I wanted used and then figured out what I really wanted. But you need to first decide where and what type of riding you want to do. Road, commuting, mountain, combination etc. Have fun with the research!