I think you should give the BRCA website,
www.brca.org a good looking through, as that covers all your insurance and club questions. There are videos and guides on setting up clubs and also a list of clubs by area and what classes they cater for, along with shops to.
From my experiences clubs charge anything between £10 and £100 a year for membership, then there's a charge to use the track on race or practice days, varying between £2 to £10 for a meeting or days practice.
With regards to timing equipment the main one seems to be BBK / AMB while there is also an infra red system that MORErc use with great success and it's only a few hundred pounds compared to thousands. Probably best to pm Benh about the infra red system.
If your running a club within a shop it would be worth while checking out what an insurance company can cover you for.
As sosidge says, you should be the ones working out what people should pay, afterall you'll be the one paying the bills and income has to be over and above expenditure.
In terms of business sense I'd do a load of research in the area you plan to set up your shop. Visit clubs and toy shops and ask how they are doing, how many members they have and how often they race. See what shops sell similar things to you in your chosen area and whether you could supply items by mail order over the phone or via the internet. At the present time any shop that sells stuff relating to expendable income is going through a roungh patch as people generally have less cash to spend on hobbies.
If it were me i'd be looking at the markup on spares and cars and then work out how many you need to sell to make a living, then is there a big enough market and catchment area near you to be able to sell that amount of stock. On tires, which i would guess are one of the most popular purchases from a shop you'd make a couple of quid a pair, so you'd need to shift 10,000 pairs of tires to make £20k and then you've got to take all your bills out of that.
My advice,
1) Find an accountant that will do a free consultation and talk to them about it.
2) Look at the clubs in your area and speak to the people that will be buying the items you want to sell.
3) Look at the competition, and if a model shop is listed as a limited company get a set of accounts off of companies house for £1 and see how they are doing.
4) Work out what you can offer that other shops can't
5) What are the trade account details, can you buy stock on a sale or return basis.
6) Have a back up plan, will a bank back you for a year or two with interest and charge free accounts, or do you have money to invest.
All the best in your chosen venture.