Yes. Why not? But go for (i) family, (ii) friends, (iii) friends of family, (iv) friends of friends to get your Guinea pigs.
The more you do, the better you'll get and the better you'll be able to identify the problem areas.
Customers like it when you can tell them things like " those end caps on the roof spars can be delicate and difficult to clean. I always take extra special care that they don't get damaged," or "as long as I have line-of-sight to the roof it's OK. But this side is very close to the fence so I'll need to do it off a step ladder. That takes quite a bit longer so the price is a bit higher."
It does take a little experience to do this.
But it's worth it as (i) you'll close more deals and (ii) you'll close them at the price that you want. When the customer feels that you respect them and know what you're talking about, you'll close more and better business.