$200-400 will go a long way toward a real nice used bike on craigslist. It will only buy an entry level bike at the store. The only problem is getting a good fit. Going shopping at a few Bike Stores and engaging sales staff will get you dialed in on the right size. It will also give you a better idea of what you want. One word of caution; the 'bent over' ride position of road bikes may not do it for you now that you are over 50. Do some test rides. bk