For a small fill station (small, continuous-duty compressor, and 2 to 4 cascade bottles), you can keep things simple and relatively inexpensive. For example, no need for a fill panel; instead, you can configure things with brass or SS pigtails, and use the valves on the cascade bottles. And no need for expensive filter cartridges; instead, you can set up your system to pack the filter stacks yourself. Stick with a single fill whip for a while, and then add a second fill whip when you're able to spend for it.
Comb the garage sales or eBay and procure a few old-school 72's (that are full at only 2,475 psig, if plus-rated). Keep in mind that these (and your cascade bottles?) will need to be hydro'd every five years, so don't get too many. Maybe only enough for you and your wife to spend a weekend diving. You'll have to cart them around in your coupe/sedan/minivan/pickup, though.
Careful: Don't get two many cascade bottles or have too much capacity. I was warned, when I was thinking of doing what you are doing, that it's important to run your compressor enough--often enough and long enough each time--in order to keep it healthy.
Can't wait to see your fill station build!
rx7diver