See thats where you're wrong.

If you don't have the money to afford a swap or a ka-t don't think you have to do it. You will end up just dumping money into a car that you'll never get back. If you do a ka-t you'll eventually need to replace your rings, pistons, and probably machine your block. Which isn't cheap.

A swap costs more then just the motor, there are lots of supplies you'd have to buy to do the swap, most likely you'll spend another $500+ putting the motor and stuff into the car.

I'm guessing if you have a car its an s13, you're obviously in high school, so my question is why do you want an rb20?