Unless things have changed this build, there's no BPO minigun, and possibly not even a militia one. If you want to run as a heavy with a minigun you'll probably have to spend some time as something cheaper to build up funds. Or just not die.
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Once you get a feel for how much things cost and how much you make per match, you can figure out how often you can spawn your heavy build per match, or just save a bunch for a single battle.
Don't forget the real game is supposed to be corporate battles, and those are going to have a lot of ISK backing them, especially if the Eve economy gets integrated. What everyone's been playing for the last year is essentially the practice mode.