Our agent (who also happens to be the builder's agent) informed us on 7/17 that there was some delays on getting internet/cable installed due to the cable company (Comcast's) fault, but that internet lines will be installed underground on 7/18/18 and we should be good-to-go after that. 

That's not simple, because there is no basement or crawl space; the tub is installed over a cable-tension slab.One possible solution I thought of would be to take out the tub, reverse it and install it a little higher, with a slightly sloped, essentially horizontal pipe running under the tub from the drain to the existing trap, a distance of maybe 45 to 48 inches.

If your only raising rents 3-5% then a small lifestyle change on your tenants part (cable, pets, vices) could likely account for the increase. 

People expect cable tv and wifi in their room. 

They are gross rent estimates that include the rent plus the cost of all tenant-paid utilities, except telephones, cable or satellite TV service, and internet service.

This is nickel and dime stuff but everything counts. 1) could you contract with the cable company to get a kickback for tenants who sign up with them2) could you sell renters insurance to your tenants and get a small kickback3) if your electric is deregulated, you could get a small kickback from the electric company for choosing which plan the tenants use.A lot of this may be regulated by the state you are in so not sure if it will work.

It's similar to how buildings have cable, internet and power contracts. 

Definitely make sure you have cable and cell service at the unit because some don't depending on where in the mountains they are located.

I've never worked with either 8 or 6-gauge cable before and I'm a bit worried about working in the panel with both.Actually, this is stupid, amateur hour.

Cable bill, pool maintenance, etc are things that cost pretty much the same regardless of the size of the home.