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

The lot shows the existing building envelope next to the proposed renovated floor plan and square foot addition. 

SW also does a virtual color consult which we have done a couple of times when were trying to compliment existing colors so we didn't need to repaint the entire house or troublesome unique bathroom fixtures. 

If you find a deal you can always make an offer contingent on selling your existing properties.

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

If the tenants are in a month to month lease and the landlord prefers it then you don't have to do anything as the lease should renew on a monthly basis, but it really depends upon the existing lease. 

It does seem competitively priced for the area.If anyone has insights into how the existing HELOC might impact the mortgage assumption or tips for negotiating on a deal like this, I’d greatly appreciate it.

Currently a majority of the existing mixed use buildings have the commercial space shuttered with the owners just biding their time until the real estate prices make sense for them to rent out or sell - or they are just asking way too much in rents for any businesses to survive for very long.

I understand home designs are pretty expensive, and cannot just be applied to any lot/existing neighborhood.

You are trying to sell him a pipedream (and, as usual, your SEO services) on wholesaling, which does not exist in NYC and the boroughs.Why don't you try to do it in NYC and see how it goes?