The property’s existing long-term tenants provided immediate cash flow, while the potential to build out the lower level for my restaurant, Arbol Eatery, and additional amenities like a wellness center and event space aligned with my vision for creating value.

Given your strong credit, rental experience, and the equity in your existing properties, you’d likely have some solid options. 

Do I need to draft a new lease with the tenant, or can I continue with the existing one?

Only those that legally existed prior to new Codes can be maintained, replaced, etc.

Buying it as an existing 4bd/4bth is doable. 

We typically buy existing debt but still good to know. 

The seller will have reduced debt capacity because the existing note is still calculated as a debt - they MAY be able to include an offset equal to the buyer payments after a period of time, BUT often the seller is surprised to find they can not qualify to purchase another property3.

Additionally, the flexibility to use the units for housing existing commercial tenants during repairs added strategic value and aligned with my broader portfolio goals.

There are less lenders that do this but they exist.

Not only to cover the existing issues but the expected issues that will crop up as the house ages.