I think you should wait until 1.9 is launched and what's gonna happen with the beetroot/chorus plant/chorus fruit. You could be the first large farm for 1.9 stuff and you can probably get a jump on figuring efficiently using single player mode.

 

Melons and more melons oh and some more melons!!!

That's just me if it don't work out I won't cry.:)

 

The chorus plant drops 0-1 chorus fruits per plant, so you can forget that. Not sure about beetroots, but probably a clone of potatoes/carrots economically. Don't think either of these farms are worth it.

 

Yeah but who knows, maybe that's someway the devs will decide to shake up the economy make them chorus fruit worth tons and only harvestable with the star shovel or something else much more interesting than propping up the already well to do with upped melons.