I frequent Melfort, that's where I usually buy stuff..

Every system you try will have flaws, or you may salivate over a feature that appears in other software.Some familiar names are mentioned frequently: Stessa, Apartments.com, RentRedi, TenantCloud, Innago, RentManager, Avail, Rentec Direct, Doorloop, etc.I recommend conducting thorough research on each app online to understand their offerings, pricing, etc.

My first tenants were paying ~1,600/month and current leases are climbing towards $3,000 a unit.

Study landlord basics, especially on what to include in your lease (going forward you will ALWAYS have a written lease).(2.5 Learn from mistakes and don't repeat them.)

One more I can add is the note investor who thought that holding the note gave him the right to determine how the subject property was managed, with approval of tenants, leases, and maintenance contracts.  

The top chart below quickly shows you what the renovated, avg and distressed homes sell for in that area on a $/sf basis over time, so if you are estimating way over the top line, you instantly know something is off, maybe you have an outlier comp on your hands, etc.It doesn't have STR data, because any STR we build must also pencil as a LTR to avoid being upside down if it doesn't workout, so we use normal residential lease data when underwriting our rentals.As for forecasts on the market, I don't do any aside from the current Q trending % at the footer of the charts, and it's really just the current Q's average data/performance held constant and applied to the rest of the quarter (since not fully done with Q yet).

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?

As for gray areas in contracts, the courts will almost always find in favor of the party who did NOT write the lease.  

i am not lawyer no legal advice but if he has overstayed it makes it easier, he is not under lease as if lease end date.

Even if there isn't a lease in place, underwriting can use market rents from an appraisal to qualify.