Talk to an architect. There may be some areas of the country where that budget would be possible.

And make sure the Architect has a realistic idea of what things cost. We had an architect draw up plans, having given them a budget of $130,000 (800 sq ft, one storey addition), and all three concept drawings were $100,000-$150,000 over our budget, which we found out once we gave the drawings to the builder. It wasn't as if the finishes, other than hardwood floors, were crazy either.

Keep saving. Or talk to your bank or MIL about financing. Your budget is too low.

Use online construct ion cost estimators to get an idea of budget you’ll need. I go to Home Depot and pick out the finishes I like and calculate the cost of these materials.