If you have mold on your walls you really should not just paint over that mold because the mold will still actually be there in the home.
Painting over mold does not kill off the mold and only covers the mold up to hide it so that it cannot be seen but after awhile the mold will come back even after painting over it.
Some landlords will actually just paint over mold as a quick cheaper fix than removing the mold from the wall and actually if you have drywall it would be just as cheap to remove that part of the drywall and replace it with fresh drywall instead of painting over it.
You can buy a new sheet of drywall that is 4 x 8 for around $7.00 to $10.00 so it's not that expensive to just replace the drywall with new drywall instead of just covering up the mold.
Mold if left to grow and left in the house can be dangerous and cause respiratory issues and lung conditions and could potentially be fatal overtime.
So always just remove the mold or kill off the mold before painting and get rid of any mold in your home before it makes you or your family sick.