I know in Portland we have a wonderful trend of additions like the carriage house called ADU's. For many of my clients it has been an exceptional boost to the value of the home. I will point out that one of my clients did an ADU similar to a carriage house and listed it on Air Bnb and received rental income for it. When the client went to sell the home she had an excellent track record of rentals and was able to sell for a higher price
However I think that some of the things to be considered here are will the 900 sq ft addition to your home include a new bathroom? Because that will effect the value greatly. Where will the addition be? A lot of contractors can also advice based on value.
In either way Good Luck!
Contact a local Realtor with Experience and they will show you what exists in the area, what sold
etc. and give you the very best advice. If you need a recommendation get back to us here.
Most Sincerely yours,
Edith Karoline Jasser YourRealtor4Life with @Properties
Working always in the very BEST interest of her clients, buyers, sellers and investors alike
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