Depends what the rental fee is though doesn't it NBs? I would've thought you could cover the costs of a bike over 8 races at what? Let's say a build cost of £3000-ish, run it for a couple of years which would work out at say £300 a race, which should cover a bit of maintenance as well. Obviously, there would need to be a hefty credit card deposit to cover a 'you bend it, you mend it' clause which would obviously have to allow for the possibility of total destruction.
I asked the question some time ago whether it would be possible to do a bike share for those individuals strapped for cash. After all, if people are talking about £4-5000 for the bike and a season of eight races, that's quite a chunk for an individual to find, but a syndicate of four people could share that and each compete in one round. Obviously no chance of winning owt, but getting a taste all the same.
Then I thought, well would you want to go to all that expense, plus the admin hassle of getting ACU qualified with your classroom and license, just for a day's sport?
Doesn't really seem any way round it, even cheap racing is expensive.