There's sooo many options. Really depends on what you like best/your goals.

BUT...
If I had $20K to start a business, I'd be buying super double co-doms. I love Sterlings! You could also go with super-blasts, killerbees, x-X-leucistics, etc. With these you will of course still get lower end morphs but no normals. Keep a few select animals each year. In two-three years you could end up with those quad morphs. Expand with the money you get from these.

And as mentioned, you can't go wrong with pieds. Clowns are also a favorite of mine(hopefully I'll get one this year, fingers crossed). The super discos and paintballs are pretty neat too; however I don't know what these cost at the moment.

I'd also get a hidden gene woma to start working into some projects. Gotta love those infernos and enchinfernos!

***Big thing here for me is the quality. Shop around and take your time. There are tons of animals out there. I'll spend more $ on a younger quality animal than I would an "eh" breeder size animal any day.***

Just make sure you can sell to the average person. If you get a bunch of $20k plus animals and no lower ends you won't make as much. Selling 10 @ $2K just seems easier. Of course, this is from the point of view of a 22yo that's just really getting into the whole breeding side of things. You have to take what sounds best for you and figure out what works. Good luck!