I'm trying to determine if it is worth my attempting to fix the foundation (and possibly adding an in-law via garage conversion) or selling "as is" for a high discount. 

I just started a flip and finally found someone able to get it done adding a bedroom and bathroom in the basement as well.

#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.

Trash,, is a constant issue,, notify tenants,, properly dispose of,, add containers if needed.. let tenants know any trash not put in cans they will be fined,, I've dug thru trash found envelopes to tenants,,taken screen shot and they get 25.00 fine for not getting it in the bin.... don't be surprised if neighbor is one to call that complaint in.. 3.

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

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 ..."

She added that there really is no "right time" to start and you just have to do it.  

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.