How many man hours to build a small house, 2500 sq ft?
When I constructed my house which was a single story (20 feet x 30 feet) and approx. 600 sq. ft. it took about 4 months until it was 100% completed . The only labor I paid to have done was the concrete floor. This was for two people working 8 hour a days x 6 days a week for 4 months.  48 hrs./ week x 4 weeks = 192 hrs./ month x 4 months = 768 hrs. x 2 people = 1536 total hours. Or it took one person 1.28 hours per sq. ft. If you want to get an idea of what the national (in the US) average cost is for any phase of construction Google (or purchase) "National Repair and Remodeling Estimator" by Albert S. Paxton. Published by Craftsman Book Co.. It comes with a CD for calculating an estimate. It also breaks down every phase of construction A-Z giving hourly wage, time for completion, material and supply costs by job location, etc..