Solid wood doors change how a house feels immediately. They shut down noise between rooms, hold heat better, and eliminate that cheap hollow rattle every time someone closes a door. Replacing every door in the house usually takes a carpenter two or three days, and winter is the best time to do it. Trades are looking for indoor work, and suppliers mark down interior lumber to clear inventory.
A full set of solid doors runs around $3,500. Get quotes from at least two local carpenters before you buy anything, because installation costs vary wildly. Once you have your numbers, you can spread the cost over a year without paying interest.
A 0% intro APR is a repayment deadline, not free money. If you still have a balance when those 15 months end, the standard interest rate kicks in on whatever is left, making those doors a lot more expensive.