You can run your rig/ac off of a house current, usually 120 volt / 20 amp via and adapter. But, the minute you start turning on other items in the rv, or other items in the house/garage on the same circuit as the one your pluggen into, your probably going to start tripping breakers, either in the rv or the house.
Your best and safest option is to simply run a dedicated 120 volt / 30 amp line on it's own 30 amp breaker. Run it to an outside wall, install a waterproof outlet box, and your set to go. Plug your unit in and run the whole thing.
I did this on our house and the total for all the material was around $75.00, which is less than a good 10 guage 50 foot extention cord and a 30 amp rv plug adapter. In the long run this is tha safest way, don't have to worry about any extention cords heating up, ot tripping breakers.