I just purchased my first rental property and I'm not to sure what website or app would be best to collect and keep record of rent payments.

As far as what the units are renting for, I would ask the seller for his records.

How can I proceed to get this on their credit record?

If elevator you need to check service records.

I used to find this information on the County Recorder's website of whatever County the property is in.

I understand this does not answer your question but it is an important factor I thought I would share since im currently in a situation with an hoa auction purchase.Make sure you do a lot of Due diligence on it.Most county records are public information type in the parcel number most liens should appear. contact a title rep and see if they can dig a little into it.

How do I go about updating the new square footage in the records, at least by the time I sell or advertise as rental in the future?

It was at the time my personal record year, and with rates up obviously that can't have been based on refinances. 

Orlando was literally built for tourism and already has specifically zoned areas and great resort communities with proven track records without the fear or local authorities or an HOA to take it away.Happy to dive deeper into this with more specifics if needed, but hope this has some value!

All real estate transactions are public information in my state so the County Auditor website has property information as well as the recorded owners.