Hi Jesse. Welcome to TFF! I am in the process of doing the same thing, although I can't seem to force myself to specialize...I am breeding fancy guppies, platies, angels, African cichlids, and cory cats. I am also on a budget (got 3 kids and a mortgage), so the fish stuff I have to be creative with. Here's a few things that have worked for me...
Check out yard sales, rummage sales, whatever they call them in your area...an excellent place to get good used equipment and tanks. Just check everything over well before you buy. Sometimes a tank with a minor crack in it can be repaired with a bit of silicone fairly easily, and you can usually negotiate to get these for next to nothing. Some LFS have an area set aside where they sell used equipment. If you don't see it, ask. It may be hidden away in the back room, but they will sell it if you are interested. If you still have a hard time finding tanks, consider non-aquarium vessels to hold water. Rubbermaid storage totes are great for this and come in assorted sizes. If you need something bigger, check out farm supply stores. One near me sells 140 gallon stock tanks (for watering horses and cattle) for around $45. I even knew of a guy many years ago that had every room in his basement filled with old bathtubs, chest freezers, wash tubs, and anything else he could scrounge from the dump(in other words, free!) that would hold water and he raised an incredible amount of fish.
Livebearers need to have large amounts of their water changed frequently in order to achieve maximum growth. With this in mind, your filtration doesn't really need to be anything extraordinary, as wastes will not have time to accumulate. I would recommend going with the old-fashioned type air powered box filters. If you are going to be running several tanks I would suggest getting as big an air pump as you can (instead of using up valuable outlet space on multiple small air pumps). My favorite so far has been the Rena brand, I am currently using the 400. These are also amazingly quiet! If you are going bigger than this, I would recommend the Sweetwater Blowers (but here goes your budget

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5 gallon buckets come in handy for a variety of uses. I use mine when doing water changes and also to transport fish I am selling to the LFS. A good (free!) source for these is a bakery...most of them get cake icing and/or donut filling in these buckets and throw them away all the time. Be sure to clean them up real good as the icing usually has a lard or fat base. Also Folger's coffee is now coming out with a plastic coffee can that has a built-in "handle" on the side, these are great for acclimating fish, scooping water, or thawing frozen food.
Instead of individual tank stands you can build a "rack" to set your tanks on (and have them two or three rows high to save space) out of cinder blocks and 2X4's (or 4X4's if you're using bigger tanks)--pretty economical and you can put them together rather quickly.
I also use shoplight fluorescent fixtures and 4 ft. bulbs for lighting my tanks rather than each tank having an individual light over it. These are really cheap at Wal-Mart hardware dept. or other such similar places. Anything I can do to eliminate the need for more stuff to be plugged into valuable outlet space is good. This also pertains to heaters. I don't use them, just keep the fish room at a temp that is comfortable for the fish (usually feels warm to me, but it's their room, not mine).
I hope this helps and was the kind of stuff you were asking for. Feel free to PM me if you have any other questions.