Advice for a Frag Tank

[bluesox68]

So I would like to build a frag tank, hoping for income generation. I almost invested in a frag setup but I decided with the wisdom of my wife, to start smaller. I have a 20 G and I'm starting with that.
Is there a real possibility to actually generate a small income with a frag tank?
I understand because I'm starting so small that at this point it's more trial and error. But I wouldn't mind getting people's advice on do's and don'ts in accomplishing this in the most simple and cost-effective way.
ie. What are some fast growing frags I could look to get?
My short term goal would be to fund a larger frag setup down the road, ultimately being able to generate a more substantial income.
I'm not looking to retire on this LOL, but it's a passion of mine.
Please feel free to send any advice my way! Just some info: My current display is a 40G tall with 20G sump/refugium, and I was hoping to utilize my system to help kick-start my frag tank. Thanks!!