Congrats on wanting to become a cyclist! Unfortunately you are asking for two slightly contradictory things though- a bike that you can train on and get through and enjoy a 565 mi/7 day ride and one that's under 400. Sure you could ride the $200
Walmart special but the chances of it fitting correctly so you are comfortable and then actually mechanically performing well are slim. I want you to enjoy your experience, not dread it.
So number one piece of advise is to go to a local bike shop- state your goal of doing the AIDS ride and see what they suggest. If they are at all condescending or trying to sell you a $2000 bike, move on to the next one. Under $400 is probably unrealistic but you can get tons of bike comfortably under $1000. Other things a local bike shop should provide is tune ups on the bike you purchase there and often they offer basic mechanics seminars such as how to change a flat tire. Take a good look at
www.specialized.com. Check out models such as the Sirrus, the Dolce, and the Sequoia. Remember that the msrp are not absolutes too. BTW- I don't own a Specialized just think they have the best options in a serious beginner line.
Accessories are also often discounted with the purchase of a bike- in order of importance for safety and comfort 1.
helmet 2. bike seat bag with space for spare tube, tire levers, CO2 cartridge, cell phone, money, small multitool(these things really don't take much space) 3. bike shorts 4. gloves 5. bike shoes/pedals. A helmet is not really an accessory- it is an absolute whether you are riding the streets or a local bike path.
Instructor/coach- not needed. You can figure out what you need to do with the help of books and the internet training plan wise. But joining your local cycling club(the fee tends to be nominal) might be a very good idea. They have organized rides that you could use for training all the time during cycling season(here in the Northeast that's April to Nov) plus it would allow you to meet like minded people. These often include beginner rides that will work on things such as knowing when to shift to get up and over that hill without redlining your effort level and such. So coach not necessary but some things are best taught by more experienced cyclists and you can get that from a local club.
About me- I am a 4th year medical student and a life long cyclist. I raced first year of college cycling but in the intervening time have been a triathlete. My longest race distance is Ironman with a 2.4 mi swim, 112 mi bike, and 26.2 mi run. I've finished 5 so you could say I do some long distance cycling. Yes, I'm a competitor but would ride even if I wasn't. It's my passion so I tend to ride more expensive equipment and I have 4 bikes ranging from a $450 single speed/fixie to a full suspension mountain bike to a carbon road bike to the custom titanium triathlon bike I have on order.
Biking takes more of a start up investment than running if your goals include doing longer distance rides. A bike under 400 would be adequate for 10 miles on the bike path on weekends but you will struggle with it for your eventual goal. I am trying to be encouraging but also realistic. More questions feel free to ask
