Worst that can happen if I give keys to check the house before accepting the quote?

[RageSloth]

A tradesman wants to measure the place up (it's one room), and I have built rapport with him, but still feel it's really weird that on my first bigger job from him he is now asking for keys before ive accepted a quote! So whats the worst that can happen, can he become a squatter for example?

How paranoid am I to consider legal ramifications here? I mean can a quote be considered a form of contract to work when it's accepted? So to hand over the keys before then seems dangerous.. right?
Thanks all!

[dslippy]

Establish the precise reason for wanting the keys, and, if you then wish to go ahead, fashion a receipt for them on that basis.