I am another newbie with just 2 R4s. Had them for just 5 weeks, with just one for the 1st week.
So far I have been rewarded/paid 0.4786 btc (thru block # 454915). With both R4s running, I average about 17.4 to 17.5 THs.
Total actual rewarded is $502.64 USD, with todays price its up t around $590.00 or about 17% profit just based on the current value.
Alot of your return obviously depends on your electric cost, mine are relative low sine I have 100% solar on my home. I expect around $100 - $125 electric bill after by unused solar reserves each month. (my direct elec is 6.8 cents / kWh.
So for me, (so far) I expect with around $500 per month gross btc, and say 150/mo elec, so I will be netting $350/month. I should have my R4s paid off in another 9-10 months (if they keep running at 100%).
I just hope future months mimic February and the btc price at least holds steady, even though most predict significant increases.
Bottom line, for me after just over a month, is that I have no regrets for becoming a small home BTC miner..especially at KanoPool!!
R4s are pretty energy efficacy as well as the s9s so I should hope you pulling in profits from 2 r4s running even if not on the best electric price rates. They should still be pulling in a good profit.
S7s on the other hand use more watts then an r4 and a lot less hashrate. So on the s7s it comes down to what some ones electric rates are and for btc price to stay high to be able to break even or on a good month when luck is good to do better then break even.
this is the big boy, >400% difficulty 
% and look it is coming true.... I say the next block AFTER this one which this guy screwed up will be at 1.2% 
