The minimum openable area to the outdoors shall be 4 percent of the floor area being ventilated.Heat Source- RequirementsR303.9 Required heating.When the winter design temperature in Table R301.2(1) is below 60°F (16°C), every dwelling unit shall be provided with heating facilities capable of maintaining a minimum room temperature of 68°F (20°C) at a point 3 feet (914 mm) above the floor and 2 feet (610 mm) from exterior walls in all habitable rooms at the design temperature.

If you can save 10k/yr, you can buy a duplex with 5% down very easily depending on where you live.

The writing has been on the wall for some time now.

http://www.hardestyhomesllc.com/mikel-james-jr/The guy is great-- manages my duplex in North Chesterfield.

In all we spent about 5k on renovations including new bathroom items, pulling up carpet and refinishing the original hardwoods, freshening the kitchen, installing a "shiplap" wall feature. 

The piers are already set up under the house and there are tiedowns  with a block perimeter wall.  

The remodel will include removing load bearing walls, remodeling a kitchen, installing a shower in the master bath, carpeting the basement, refinishing the wooden floors, and finishing a roughed in bathroom in the basement. 

If it’s single family it will be 20 percent down, duplex or above (up to 4 units) will likely be 25 percent down.

Just before relocating, I purchased a duplex.

There are not many multi family homes other than singles and duplexes.