I've already learned a lot in the past few days since finding this site and looking forward to going deeper into this area!

Great that you joined the site!

Listed properties are listed on Realtor.com and sometimes 30 to 100 different web sites, the exposure is tremendous, more than you can get by yourself and locally.3. 

What is the best online rental payment collection site to use for 1-5 rentals.

Great that you joined the site!

HOA fee - If HOA fees are not paid, business will incur fines, so it is necessary to make the profit in the business.8) Marketing expense and advertising9) Cleaning and maintenance10)Commission (Expenses like commission, abstract fees, recording fees to obtain your mortgage are not deductible but rather capitalized )11) Insurance12)Legal and other professional fees(Tax preparation for business, not personal part)13)Management fee if applicable14) Points- you generally cannot deduct the full amount the first year but have to deduct them over the term of the loan.15) Repairs (Note always do repairs rather than improvements to rental because repairs are deductible right away and do not have to depreciate over few years as done for improvements.

I know there are niche sites that cover some of these, but is there one master site that does the most? 

Unfinished but clean basement.

Also, can you then sublease this apartment on STR sites like AirBnB without breaking any laws, even if the lease states subleasing is not allowed? 

I also would love the create a platform to organize the countries real estate cycles per area. like an informational web site.