Usually it's very slow that you don't even notice and roots can get in. 

When we walked through the home we noticed the laminate flooring is slightly unlevel in certain places, my only thought is that it could be a foundation problem causing it.I'm just looking for how others proceed in these types of situations, I am still very interested in this property and not scared of the foundation issue at least not before getting a quote to estimate the repairs (if this is even the problem).

One weird thing I noticed is that it was really difficult to find an attorney at first who had any experience with hard money.

After posting a notice to vacate on the door, if the tenant agrees to leave, is there something I should have them sign to officially terminate the lease and legally take back the unit?

As there are no leases, you would need to follow the New York procedures for terminating month to month tenancies (timely notice, etc). 

I have noticed a lot of land-lords include their email as well. 

We also have no land transfer tax, or rent control, which is a big advantage in multifamily (5+ units), as you can improve the property, raise rents to market value with only 3 months notice, and suddenly the building is worth exponentially more.

I have noticed a lot of construction in many neighborhoods in the city as I pass through often to see friends.

I noticed you live in brea and actually I work in brea and live in Fullerton!

Issue a Notice To Quit to the "tenants."