If you think your new living situation will be more permanent, look at adding an accessory apartment, which has a separate living and sleeping quarters, a place to cook, and a bathroom. It can be located upstairs, in the basement, over the garage, or even in a structure separate from the main house. Before you build, check with your local zoning authority to determine whether your town allows accessory apartments, and if it does, what covenants, conditions, and restrictions apply (there may be minimum or maximum size requirements, for example). If an accessory apartment is not permitted in your town, you might be able to ask for a special use permit.
Costs vary widely, but setting up a garden apartment in a home with a walkout basement or a split-level will be easier than raising the roof to add a second story to a ranch-style home. You should also discuss how much storage will be needed, whether additional parking is necessary, how private the entrance to the new apartment should be, and whether a studio layout will work or if more rooms are needed. When your daughter eventually moves out, you can rent the apartment for additional income.Learn more about building a new apartment:
How to Finish a Basement
How to Design an Affordable Attic Bath
4 Tips for Finishing an Attic
How to Install Attic Stairs