Also, if you are licensed, you are held at a higher standard when it comes to selling property and other things and I don't want the extra liability.

#1: You maintain control over specific value-adding potential. #2: You ALWAYS have to pay full market value for shares. #3: You're MUCH more reliant on the whim of the economy with shares, vs. property.#4: People always need to live SOMEWHERE (even you).#5: It's much easier to BORROW to buy property, vs. shares (and STILL obtain positive cash flow).

Another way would be to look for similar rental ads on Craigslist or ZIllow to see what other properties are looking for...From a negotiation standpoint, you should have put in your offer already including the roof and HVAC since you already know about them.

I have a 2 bedroom/2 bathroom primary residence that I bought with the intention of renting out the extra room.  

like how much down payment would be added to calculate a positive income for a rental property?

I've heard of this kind of thing happening so I'm extra careful when I rent because I live some distance away from the properties I manage.

This income will be added to your regualar w2 or business income to determine your total debt to income ratio (DTI) against your debts and monthly mortgage costs.To calculate your net rental income, your total rents collected for the year are added to deductible expenses (taxes,insurance, interest, depreciation).

Run an ad in the paper ..."

Four years ago a little idea started developing: I wanted to make extra income without a second job.  

Don't just target the obvious CL ads, go after the indirect indications that there is a house to sell, such as an estate sale.