its a tricky one. involved with something simalar up this end.
as with everything involving customers the customers themselves are the biggest problem. inside under cover storage fetches good money. the profit is with the proper big money classics not your average enthusiast.
letting customers into the shed is a BIG NO NO they can walk round under supervision, they defantly cannot drive there cars in the shed or work on them.
a ramp they can use by appointment is full of win however, renting them hand tools is full of fail. charging them to fix there cars whie they
helpget in the way is full of win.
haveing a heap of batteries for sale is full of win
haveing fuel avalible. espectaly 20ltr drums of proper 4* sold by the drum is full of win
transport / recovery can offer much profit
you need a LOT of cars to be stored with you to make it worth doing imo. insurance premium is absolute BUM RAPE as for profit it dosent make much for me but it pays in perks and i don't actualy do any work to do with it

chould make quite reasonable money if did teh work yourself