well, if your flight is free, you’re off to a huge start. staying at cheapo highway hotels in the middle of nowhere was usually about $40-50 for a night. once a week, i figure TV, a hot shower, some laundry - it’s worth it. camping in some little towns is a matter of pitching up at the local Lion’s Club park, or whatever, and dropping $5 in the bucket. at provincial/federal parks and private campsites it was more expensive. (personally, i don’t suggest the private campsites - these days they’re full of people sitting in huge RVs watching TV with the air conditioning on. tell them you’re camping and they think you’re a dirtbag hippie or something.) then of course friend’s places are free, though usually i’d pitch up with a bottle of wine or something.
food was cheap - mostly just groceries. i’d have quaker oats most mornings, and then dinner would be pasta, rice, soup - something boring like that. i’d pay for lunch on the road if i had a good momentum going and didn’t want to stop too long. and of course i ended up buying a fair deal of juice/pop/water/chocolate milk on the road, so a few bucks a day for that. of course, i’d also treat myself to hot meals once in a while, and it’s nice not to do your own cooking all the time. plus, i really think if you’re riding all day, you really do need a big steak once in a while!
the rest was just odds and ends. i’d clean my drivetrain once in a while, but carried my own lube and grease i think. i bought a new cassette toward the end, and had it installed. i had only 1 flat tyre, and carried a folding spare. decided to buy a new spare to replace it, and always carried lots of tubes.
i should note that i owned all my own gear already. i’d done lots of camping, so i had tent/stove/bag etc and didn’t really have to buy any new kit. i’d also been cycling for years, so had most of what i needed. bought a new pair of bibs, maybe some socks. . . not much.
sorry i can’t put a $ figure on it off the top of my head, but hopefully you get the idea. first i think you want to decide your basic “capital costs” - basically, the gear you need, since your flight’s free. next, you can start tuning the ‘operating costs,’ and figure out how much you could afford to blow on hotels, food, massages, etc. . .
-mike