Since the weather in Chicagoland is nearly identical to MKE area, maybe 1 degree warmer average annual temp if that, I'd certainly assume that any property that has electric service also has a gas line running to it, unless you're in a rural area where they'll often have a big propane tank sitting outside someplace.

My goal is to not be a "shark" in this industry but i just want to have everything running by a certain age then relax.

Kay Beard w/ fulton bank is an absolute shark....PM and I'll send you her contact info. 

I'd bet the price for any station for sale just jumped up 10-15% like the remaining gas in tanks... if there is any left. http://www.wral.com/nc-stations-run-out-of-gas-aft...

Make sure you get a well respected partner/mentor as there are sharks out there... good luck!

Are done 4 furnaces 4 hot water tanks?

They would also check percolation rates as part of that which influence design and tank sizes.  

If I put in 1 heater then I have to pay to heat the water (unless I bother to charge the tenants a proportionate amount every month which is a hassle in my mind), but only have one tank to buy.

Start by getting a credit card and pay it off every month only buy a tank a gas or so so you don't run the bill up.

I have 4 separate furnaces and one central hot water tank.