Here's a tip that I've learned being in this business for over 40 years. The key is in the buying, not selling. Value adds are always a great opportunity to generating additional more money.
If you have extra space on your property, consider applying for an ADU. If you have a basement or attic, consider converting it to usable space and attach it to the unit above or below. While they cannot be considered rooms, they will bring in an additional $$ each and every month.
If you have a mixed-use or multi-family, consider adding a laundry room, vending, etc.
Then you look at your expenses to see what you can pass on to the tenants. Transfer the water meter to their control. Transfer landscaping and snow removal to them as well.
Do you have a single-family house with a separate garage? See if you can add livable space on top of the garage.
These strategies help two fold. One, it can solve any short comings in the income. Two, it makes your property more valuable with the value-ads.