The majority of investors I work with after using this form more or less break even on the rental business which makes it a non event and very little impact to your debt to income ratio.

Not sure if I'm missing something.Look at it from a perspective of even if your tenant is sec8, majority of the time they still have to pay 30% of the rent.

One of the lease for a rental is about to expire and would like to change from single family to rent by the room and try, to market for regular leasing we normally go to Zillow and advertise for free, but for rent by the room not sure which of all the sites out there will be the best option(s), some of them are for free, majority pay a monthly or anual subscription ($99 to $200).Do you have any guidance on which to select?

Over and over, you can be constantly evicting and replacing appliances and doing major repairs.

For example, they lost a fairly major battle when they tried to argue that only licensed professional can manage short term rental properties. 

:Class A Properties:Cashflow vs Appreciation: Typically, 3-5 years for positive cashflow, but you get highest relative rent & value appreciation.Vacancy Est: Historically 10%, 5% the more recent norm.Tenant Pool: Majority will have FICO scores of 680+ (roughly 5% probability of default), zero evictions in last 7 years.Class B Properties:Cashflow vs Appreciation: Typically, decent amount of relative rent & value appreciation.Vacancy Est: Historically 10%, 5% should be applied only if proper research done to support.Tenant Pool: Majority will have FICO scores of 620-680 (around 10% probability of default), some blemishes, but should have no evictions in last 5 yearsClass C Properties:Cashflow vs Appreciation: Typically, high cashflow and at the lower end of relative rent & value appreciation.

You should know how you can contest your assessed value, especially if you are buying the property for below current assessment.You should understand if there are any tax abatements available today or in the future.There are real estate tax consultants in basically all major markets, or your real estate agent can likely help with some basic questions, as well.

Night Before the Exam dot com is a good state study test if they have it for your state.To be clear though, the majority of what you learn in the class is not used by residential real estate agents in practice.

The above two are your major liability determinants.  

Thus, I am interested in suburban space near major cities, not the downtown inventory that is trading for pennies on the dollar, but often involve massive office complexes that will have huge holding costs until they get leased up.