Like always? That sounds pretty strange these days actually....many painters are sitting at home and would love for the phone to ring. It depends on how much patching is involved and how many coats you are wanting. A room that size generally for me is a 4-6 hour job for two coats with minimal amount of patching/repair (few nail pops, patching of picture holes, etc) which would cost around $270 labor only.

It rings alarm bells for me too, neighbor or not, it's really in your best interest to get a price before he starts, you have more to lose in this scenario using a neighbor and/or friend. Should he bonk you on the head with a huge quote when it's all said and done. You risk having hard feelings and still have to live next to each other and maybe even a friendship etc. Too risky. So either tell him the most you are able to pay or get him to commit to a price ahead of time.

I would also not take it for granted that he intends to do a professional job (ie: patching holes etc) although that seems like a natural thing to do, not all who paint, paint equal. so again, your expectations should be spelled out ahead of time, then there is less room for any misunderstnadings.

and fwiw..I've seen people who advertise in this area to paint a room for $100-$150. so it could be a regional consideration as well.

Maybe you could post something on your local Craigslist asking other home owners to share what they have paid?

just my 02 worth....good luck..