You can easily use one pot and one burner if you modify another cooler for your hot liquor tank. Here is a really flexible system that I would recommend if you are batch sparging:
MLT: converted 10 gal Rubbermaid cooler (see my sig for construction details)
HLT: 5 - 7 gal cooler, converted the same way
boil kettle: converted keggle
heat source: propane burner, such as a turkey fryer
chiller: 50' immersion chiller or 25' counter-flow chiller
extras: if you want to do step mashes, a steam injection system (see my sig for an example), temperature probes, etc.
A cooler-based system has some real advantages that I think people sometimes don't give full credit to:
- they are inexpensive
- they are easy to assemble and don't require special tools (e.g., welder)
- mashing in a cooler makes it very easy to hit and hold a mash temperature, and the heat stays very uniformly distributed
- the system is light and easily portable
- does not require a separate brewstand
- allows one to get away with using only one pot and one burner (the most expensive items in the system)
- you generally don't need a pump because a cooler full of water/mash isn't nearly as heavy to lift as a full keggle (so less expense, one less thing to clean)
I suggest two different sized coolers for flexibility. For example, if you are brewing with a small grainbill, use the 5 to 7 gal cooler for your mash tun so that you have a good grainbed depth. If you are brewing a bigger beer, use the 10 gal mash tun and the other becomes the HLT. While you are mashing, heat your sparge water and put it in the second cooler. Lauter directly into the now empty boil kettle, and start heating, and conduct your sparge. You will only be limited if you want to do a really big beer and you need a lot of sparge water, in which case two 10 gal coolers might be a better setup.
As other posters suggest above, if you decide you want to change your system around, the components here are almost completely recyclable. Those round coolers make excellent fermentation chambers for lagering (just add ice), and they hold a corny keg really well for deck parties. So you won't really be wasting any of your investment if you still want a big 3-tier herms system down the road.
Disadvantages of a cooler system:
- poor LCF (Look Cool Factor -- yeah, the coolers aren't as impressive as a big, shiny SS herms setup)
- can't direct fire them (but you can use steam injection which is just as easy, and has many advantages as well)
- probably some others I am not thinking of right now
Anyways, that got long -- sorry. Just my $.02.