With the mention of improvements such as water for a washroom, you may want to check with your insurance. I have a parishioner who has a shed with a bathroom in it and it was flooded two years ago. His car insurance covered the cost of the cars, but housing/building insurance would not cover the building and contents because it had a bathroom and was considered living space. So he is forced to pay for flood insurance on the building and contents by the bank and the insurance company will not pay because there is a bathroom in it. I don't know if you live near water, but I would check with your insurance to see what hoops you have to go through to get it insured and what improvements would negate your insurance.