Jim, why don't you do a search on eBay for inverters? I think that there are thousands of them available.
Your approach for a temporary setup is fine, but you shouldn't spend much on a no-name inverter. You will be soon carrying it as a spare when you figure out what they have to offer.
A caution about heating or cooling from batteries. Heating and cooling loads are the heaviest users of power in most people's lives. Most people have very little idea how much power they use. If you don't make an effort to learn how much power you want to use, your dead batteries will start teaching you.
A golf cart battery will store about 1 1/3 kwh, of which you can repeatly use around 1/2 kwh hour without shortening the life of the battery very much. You're going to need some deep cycle batteries for your conversion anyway, so why don't you just pick up two of them for your temporary power storage? Car batteries are NOT suited for this use.
Then, you can use a kwh between charges, and you will start getting used to life on battery power. It's different.
For what it's worth.
Tom Caffrey
Suncatcher
Ketchikan, Alaska