OP after a quick(and pretty rough) calculation I think for about $4000-6000 you can make yourself 3-4 rigs which will net you about $400-$500 in total every month. Now if you could work something out to pay less for power you'd be swimming in money. These new electricity meters are often checked wirelessly and can also have their settings changed this way, without need of opening it up and breaking the seal or whatever. Just a thought
Where are you coming up with those numbers? This guy, blockoperations, is a pretty big miner operator and on his website he has some costs on building a rig - 6 GPU for 2,250. He includes a break down of the components and prices. So, for 6k that would only put you at 2.6 rigs. Maybe it can be done cheaper than blockoperations, but at the same time quality components don't break down as fast.
https://blockoperations.com/6-gpu-mining-rig-amd-rx580-intel-lga-1151-ethereum-zcash That's if you insist on going to 6-card riser rigs.
For $6750 you can easily build 5 and possibly 6 no-riser 3-card rigs, and if you go with Phillipma's favorite Biostar 4-card board you can probably build 4 or 5 4-card rigs.
The smaller rigs have the advantage that if something breaks, you lose half as much hashrate - at the cost of slightly more power consumption and *usually* somewhat more space needed.
You also get better reliability IME, risers have a bad habit of having issues and 6-card rigs can be a pain to get working reliably since the drivers aren't really INTENDED to handle that many cards.
You also don't NEED a "frame" for a non-riser rig, which saves back some of the money (as does not needing risers) you have to pay for 2 MB/CPU/RAM/drive sets (PS is a push, one big with a GAZILLION connectors to power the GPUs AND the risers vs 2 half-size "normal number of connectors needed" is pretty much the same price on high quality PS).
I'm NOT impressed with a couple of the blockoperations picks:
Not real fond of Antec PS, and their plat PS is *BARELY* more efficient than the EVGA 1300 G2 "gold" or the Seasonic X-1250 "gold" models while costing noticeably more.
They're paying too much for their ram - 4GB is plenty for most mining rigs, and DDR4 still carries a price penalty over DDR3 (but if you INSIST on Intel, most of their recent MB are DDR4).
I'd suggest 2GB but it's almost impossible to find 1GB SIMMS any more (and they've gotten kinda expen$ive).
Buying the OS on a stick/SSD might make it easier to deploy the rig, but does waste a bit of money over just buying the stick and doing an install of a FREE OS (even the free mining-specific OS distributions).
With all that said though, that site DOES give a good "this is a place to start" on the cost and choices to make for a 6-card riser rig, and their total cost is pretty reasonable all factors considered.
As far as electric cost goes - before I moved into my current place (fixed-price electric built into the rent by negotiation with the landlord before I moved), my last full-month electric bill was for $394.86 all up, on 8640 KWH used, or just a bit under 4.6 c/kwh
I figure about 13k of that was mining gear.
Buying hashrate from Nicehash *can*, sometimes, make more than owning - but most of the time you're fighting other folks that probably don't HAVE any mining gear and you end up paying more than you would make from pointing YOUR gear at Nicehash, much less what you can often make by pointing it at even MORE profitable options.
He goes that step further and provides a whole package. 
