One of the biggest mistakes I have seen less experienced investors do when choosing their first one or two flips is thinking they can save a lot of money by doing a lot of the repair or upgrading working on their own compared with paying a licensed contractor to do the work and mainly because a person doing the work themselves are not as experienced at doing good quality work and frequently will take a lot, a lot, a lot longer to get the work done and if you are financing your deal they you will end up paying a lot more in finance interest and still maybe end up with marginal instead of good quality work and you are only delaying the date for flipping , reselling, or being able to get a property rented.

As in a lease option?

You can SELL a tenant-occupied home and the tenant's existing lease transfers to the new owner.

They provided security upon lease signing. 

You will need to do Due Diligence on the commercial tenants, review the leases and try and strengthen them to mitigate the risk.

So I have a question on how to handle an upcoming lease renewal.

When I asked her to provide a copy of the lease, she sent one that expired a year ago.

Collect deposit during lease signing.

He who talks first frequently loses.

@James Edwards first realize you have to honor any existing lease, even a verbal one.