His rates are a little expensive for my tastes. I suppose that is to cover any possible damage arising from use.
I think the best way to "rent" equipment is to buy it from a second hand shop, with an agreed price if you return it within a specified period, depending on condition. Or just buy it without any agreement, and try your luck when you resell it back to the shop. That way the shop does not run any risk, you get to try the lens for whatever period you like, and even keep it if you change your mind about returning it. You trash the lens, you keep it. The shop also makes some extra income for the time the lens was being used by you instead of lying idle in the window display, and they get the lens back in the end. The difference between your buying price and your selling price is basically the rental fee you're paying.
There's an 85mm 1.2L and a 50mm 1.0L lying in the window in Camera Workshop.... No DSLR's though.