They’re older and not great with technology so I pretty much did all the paperwork and e-signatures and document submission etc.

It is very beneficial to live in your STR for a few days before listing it for guests.

Unless you somehow documented the break while the old tenants moved out it's going to be difficult to prove fault.

Now that I want to get started in REI I felt that learning little things here and there pertaining to houses will be beneficial in the long run.

Get a signed document from the seller saying the tenant is not paying

They will want EVERY single document that you have, have patience because the good ones are often thorough. 

By the way, an LP is not typically a stand alone document...it is “notice to the world” that an actual law suit has been filed, and filing of an LP without filing the law suit would be considered fraudulent.

It will be recorded by title company as first lien. so my question is  who keeps the Original signed documents after recording.It will be kept with title company, or as a lender I should have original documents.I did lending before at that time I didn't get original documents , title company just email me digital signed bundle of all documents.What is benefit/loss(if any) if I as a lender insist for original documents.Thanks

If you would like to do it long-term and turn it into a business it would be beneficial to eventually turn it into an LLC, but it is not necessary to start out.

So I now have options, either pay more to avoid the PMI or sign a document.