leaky roof repairs/ where to find contractors

[Luke H.]

Rental property: Tenants found 'wet spots' on the ceiling in 3 different rooms. I've called out 2 different contracts so far. We have been in the attic and can clearly see the 2 areas where wood is rotten (probably 2- 4 long), rest of the wood looks nice and dry. 

A) Contractor A bid $1,000 to fix 2 leaks, replacing 10 feet of plank wood 2 pieces, replace shingles, place plastic cement and fiber glass along the valley. 1 year warranty, $300 advance, $700 when complete. He had a bandit sign that read "leak repair $150.00", so I estimated total repair of 4 items would be $600, but his bid is for $1,000.00

B) Contractor B bid $700 to fix 2 leaks, replacing 10 feet of plank wood 2 pieces, replace shingles (no plastic cement). Payment at completion, 30 days warranty. OR $3,000, to overlay new shingles on top of old shingles.  This guy was recommended by someone I know, but get the overall feeling he really wants to sale me on the overlay.

I plan to get at least 2 more quotes. I'm looking in Craigslist , and have tried thumbtack. 

Questions:
Where should I look to find reasonable contractors, all types?
I'm in Houston, Texas. House on pier and beams, house shifts. I plan to have the house leveled, so I'm wondering if I should do that first?