(Some tenants in college towns try to supplement their college experience with sub leasing the floor..

It's always just been supplemental income, though. 

Books and podcasts are great supplemental material, but they cannot be a substitute for actually going out there are diving right in.

So now I'm posing this as a supplemental question to the original.

Add a closet, proper windows, and supplemental heating.

This job is typically 100% commission, but being that it is not an entry level position and I am an entry level candidate, they have offered me a decent sized salary to supplement me until I can establish a foundation in my area.

Same like in 2007-2008 HELOC became harder to get later on in the downturn.The reason i love HELOC's is because it helps with Liquidity, I would suggest all investors to try and obtain Lines Of credit sooner rather then later. some lenders will give a LINE OF CREDIT supplemental loan.

After some thought, we figured we would offer to just buy it from him, with the idea in mind that we could supplement much of our mortgage with the detached guest house.After lots of conversations with a lender, I was pre-approved for the ~$300K the owner wants, and I was able to work out a Conventional loan with 5% down, owners pays 3% towards closing costs (he’s a good guy and agreed).

But, when you purchase an investment property with the goal of ultimately using the cashflow to supplement your own income, at which point do you stop saving up cash reserves in the bank (vacancy, disaster, capex, repairs, etc.) and start diverting the cashflow to yourself?

I'd advise also having a conversation with good insurance brokers that specialize in multi-units...so you get the right liability coverage there and perhaps supplement with an umbrella policy.