If you batch sparge, you can manage with more like a two tier system, if you're willing to lift a few gallons at a couple points during the process.
I use two coolers, one as the mash/lauter tun and the other as a holding vessel for sparge water. Both go on sawhorses above the brew kettle.
I heat all the sparge water (usually around 6-7 gal)...half goes into the MLT via the bucket, the other half into the holding cooler.
After draining the tun into the kettle, I put it on the ground and drain the second batch of sparge water into it. Then I lift the MLT cooler onto the sawhorses. Usually I can get my son or SWMBO to help lift it: it's 10-12 lbs of grain plus 3.5 gal or so water, lifting it up maybe 3 feet: not that big of a deal.
I know a true three-tier system would be easier, but I have very little storage space in my garage and this is very quick and easy to set up w/ two folding sawhorses (plus no expense--my entire system, except for the keggle, was just adaptation of stuff I already had.