If you have a room (or rooms) that are going unused in your house, consider furnishing them and renting them out to tenants. If you do so, be sure to abide by the laws that govern landlords in your local area with regards to rent levels, amenities, and the like. Doing this allows you to collect a sizable check every month without any work beyond preparing the room for occupancy.
The more private the room, the more you will be able to charge for rent. If you have a separate basement apartment with a kitchen and a bathroom, you will be able to charge much more than you would if you only have a spare bedroom.
Only rent rooms to responsible, trustworthy tenants who will pay you on time and respect your property. It’s a good idea to screen your tenants by performing background and credit checks, as well as asking them to provide a reference from a previous landlord and a copy of a recent pay stub.
Services such as Airbnb can help connect you with travelers and others looking for short-term rentals. This can enable you to charge a significantly higher rate per night than if you rent the room by the month.