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. House Painting Denver Colorado
For trim and doors, start with 1 gallon (3.8 L) of trim paint for every 600 sq feet of floor space. Purchase more at the store if/when needed. Trim is something that is difficult to calculate exactly, and it is more time-efficient to simply start with less than you need, and go buy more after you have used up the first round of paint and determined how much you will need to finish by seeing how much you have painted so far, compared to the gallons used.
Plan the workforce. If you intend to not hire a professional crew, you'll need lots of help. There are many jobs to be done. First there's the furniture moving, then wall preparation, floor covering, materials gathering and prep, cleaning, and don't forget everyone will have to eat. It can easily take a team of five people a full ten days to paint a two-story (approx 2000 sq.ft.) home. Get as many people to help as you can. If some can only come one or two days, great. Maybe others can fill in. Ensure you plan with your workforce members in mind. They'll need plenty of time to arrange days away from work. Identify a few key personnel: House Painting Denver Colorado