Are you planning on doing an overflow with a sump? If you are, then it'll be fairly easy.
All you need is a small pump, a rubbermaid container, a bulkhead and contents... lights would be the only large thing to get... Maybe 20-30 if you go with regular lights.. maybe 50-100 if you get more powerful ones.. There is a huge range of different lights used on a fuge, from cheap to MH... Just what you have available.
So, if you'll have a sump, simply pump to a container that sits with enough of it above the sump, that a bulkhead can be installed to allow the fuge to drain back to the sump.
The fuge can have a sand bed and macro algae, or whatever you want..