The best questions would be Licensing, Bonding, Insurance. References will be next....Besides that, I'd ask about maintenance and weed prevention. Good Luck, Post Some Photos!
If references are provided to you by the contractor, make sure that they are recent, not a year or two old. Also, be sure to call the refs and if possible go look at the work. Seeing is believing.
The best questions would be Licensing, Bonding, Insurance. References will be next....Besides that, I'd ask about maintenance and weed prevention. Good Luck, Post Some Photos!