How can you put a dollar value on sweat equity in joint home building?

Answer 1

You may be looking for some other kind of answer, but it seems clear that after you put in the sweat, an unbiased professional appraisal (not a realtor's market analysis or estimate of value) will give you a good idea. Of course, an appraisal prior to the work would give you a reasonable comparison, given that you can adequately adjust for market changes between appraisals. If you are not in a position to pay for appraisals, a realtor's market analysis would be informative.