what i did was run a single 8/3 wire from a 40a circuit to a sub panel with 4 20a breakers inside. now i can run 4k worth of lights an a 12,000 btu portable a/c without worrying about fire, or popping breakers. now when i move i can take it all with me. there was no modification to the house other than running 1 wire, so there'll be no repairs to make later. depending on how handy you are, the location of the breaker box, the empty spaces in the box, and how hard it'd be to pull a wire to the box, you could do it yourself. extensions cords are not advisable. they are usually smaller gauged wires that aren't designed for heavy current like you'd need, and the heavy duty cords are more expensive than it'd be to just run the heavier gauge from the box. the main thing is making sure you have an open spot or 2 in the breaker box to be able to upgrade. if you don't have the extra slots in the box or an unused 220 circuit, the cords may be the only option.