Go to Etsy and search for "rental property tracker," and you will find hundreds of nice spreadsheets to track 10-20 rentals, usually for under $10.Software has extremely helpful features like online payments, marketing syndication (click a button, and your property is advertised on multiple sites), electronic document review/signing, maintenance tracking, and owner reports.

Advertising (photos and listings.) turn over costs, snow removal, and those kind of things.

I also support the point of thinking at least 10 years ahead and only buy properties your future self will be happy.

I share my experience based on truths and facts and have evidence to support them should this end up in court. 

Advertising an illegal, non-conforming basement for rent, whether publicly or privately, out right violates local laws. 

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?

I’d be happy to share my resources to support your success in the area.

I fully support doing everything you can as a landlord to be in compliance of local zoning and ordinances, so I want to use your thread as a chance to let newer investors know a really important lesson: you can call the local municipality prior to owning a property. 

While the LTV and rate aren’t perfect, it supports your scaling goals.

They will not offer that (instead relying on your advertised rate), but they will be willing to pay what you're asking without fuss as long as it is below that high threshold.