I just found some cheap wagon wheels and tires. If you buy them all seperately you can get them for less than 200 a set and they are easy to resell. For tires I was able to get some junkers from a dealership but also if needed and you plan n running an 18" wheel you could get the right size tire now and then just swap tires when you get the wheels you want.
My truck with C6 suspension all the way around has 16x8 with 4 inches of backspacing and with no brakes rolls around fine. You only need the bigger diameter to clear the calipers and rotor and you need the offset to get it away from the spindle. With the smaller rim and tire combo it lowered the truck considerably, so I had to cut bars to raise the truck up to have ground clearence.
You obviously have to remove the brakes to do this.