Ok, this admit able is not my primary profession however being in the construction industry for 37 years, having a professional background in construction management and as a licensed engineering and building contractor since the early 90's I am pretty sure I know a little bit about this subject.
Last time I checked a home builder will average 11% to 14.5% profit after all costs. This means to build a home you must borrow and / or invest about 85.5% to 89% of the FMV of the home. Now this actually equates to a fair cost with carrying costs of about 80% of a new home. As closing costs and realtor fees equal roughly 8.5% to sell and transfer title which is paid at close of escrow!
Last time I checked you have to have experience and a track record with references to borrow money to build a home. Now if you don’t have a general contractors license and you contract for a general contractor to build your home you will be lucky to make 5% in profits after all costs!
Now you don’t just pop in and build homes as there is a lot to know and if you want outside money you’d better know the industry and have a defined exit strategy.
Now I have friends in the home building industry who have great knowledge and can clearly state it’s not as easy as it looks or everyone would be doing it.
For construction cost data try RS Means as they are the foremost authority on construction costs and applications by state and the only construction cost data readily excepted by state and federal courts nation wide.
You can purchase RS Means construction cost data books at Home Depot or Lowes or directly at RS Means website.
It depends on whether you have supplied an accurate set of blue prints to bid from with a spec list of finishes or have supplied an accurate scope of work stating exact distances and locations and measurements of the work.
Someone going I think it will cost $3k without having accurate instructions to bid from is blowing smoke!