I have painted a few bedrooms myself

but I only did one at a time, not all 3-4 bedrooms together. If you don't feel fun in doing it or want everything to be "perfect" (like me), I think it's better to hire someone to do it. It is a very tiring job.
We hired someone to do the whole house painting for our previous house, including all walls (4-bedrooms house) and kitchen/bathroom cabinets. All for $2000. I think it is not bad.