Remove any outlet covers or lighting fixtures (if possible). Then scrutinize the walls for any defects. Simply fill them in with caulk or spackling compound if you encounter cracks, dents, or holes in your walls and trims. There are also tips and tricks for filling nail holes. Once done with the repair, smoothen the wall down with sandpaper and then wipe it with a damp sponge.
It's up to you. Outside is much harder because it requires more prep, patience, time, help, money and of course, effort. I have been painting my own houses and rental properties interiors for 20 years, and I painted the exterior of one, once. I then had it promptly done again by professionals who said it would have been cheaper if they didn't have to undo my work first. My advice is to get pros for the outside because everyone will see it.
Painting interior walls does not require professional aptitude, but it is still a skill that arrives with a learning curve. The most challenging part of any interior painting project is the prep work, which often involves cleaning the walls, masking off windows, doorways and baseboards, then carefully “cutting in” the paint around the edges. Once the masking and cutting in are finished, volunteers with handheld or roller brushes can usually fill in the rest of the space with little trouble.
Homeowners report that painting a home’s exterior costs an average of $2,923 with a typical range between $1,734 and $4,119. The average price per square foot ranges from $0.50 to $3.50 depending on your location, condition of your exterior and accessibility. Stucco and brick cost an average of $1 per square foot more than vinyl or wood. The average 2,500 square feet home costs an average of $4,000, though it can range from $1,250 to $8,750.