How do you give prices when bidding on interior painting jobs?

I need to know how much to charge for a 3 bedroom house that was built in the 1930's, that is in fair to poor condition. it will just be for labor. the house will need to be caulked patched and painted.

Try researching what your competition is doing on craigslist. I've seen tons of ads that do include a hourly rate. That should get you started.

My boyfriend had his home's exterior painted this summer and paid $1500, which included labor (power washing, scraping old paint, sanding, 2 coats, trim) and supplies (brushes, buckets, ladders, etc); he just paid for the primer and paint. His house was in good condition (1700 sf - 2 story).

1.00 per square foot

Should result in $50.00 per hour

Generally, you need an estimator to do the estimating. If you do not have the estimator, then you need to estimate it by yourself. A good rule of thumb is to take the house measurements or blueprints if you have any and then calculate the following;
total square area less any non paintable areas. Then as an example you need to figure out the following;
Each Gallon of Paint will paint what square area
divide your square area by the gallons of paint to figure out how many gallons you need.
Secondly your supplies...paint brushes, Paint rollers, non paintable area covering tape (electrical outlets door frames and hinges, etc), floor protectors,again figure out what you need and the costs.
Once you have figured out all your material costs, most companies do a 25-50%markup
Labor is usually by the hour and for painters ranges from $18-$30/hour depending on experience and qualifications. A fairly large house that you are doing can take a full day with 2 or 3 experienced painters to apply 2 coats. I would say a rough estimate for a house of this size, will be no less than $1100-$1300 (3 painters@$20X8hrs+Material costs and 50%markup)
Anyways, this is a starting point. Hope this helps.