Like @Ann Bellamy mentioned, my lease also specifies that all payments will be applied to outstanding fees before being applied to back or current rents.What I am unclear on, and I would greatly appreciate input from others, is whether or not I can simply send updated lease verbiage to tenants whose leases have expired (and are therefore month-to-month), without getting their signatures, or if I have to take the time to approach each of them individually and get them to actually sign the new lease.

The bank valued them at 350k which is a lot lower than expected but they are using a combination of price/sq ft, replacement cost, and income approach.

All great comments but I would like to add a different approach that gets missed over and over again (even I did this years ago) Before shooting low-ball offers through MLS listings, build rapport with the listing agent, because at the end of the day, it is the listing agent that can "sell" your offer.

And also how would a buyer approach a seller to get them to finance?

The main reason that the income approach is used for commercial properties is because of leasehold considerations. 

If you don't have a mortgage/financial pro, I would recommend approaching a handful of investors who have been successful (for more than just 12-18 months) and asking them for a referral to their "money" guy.

Fielding emails and texts are fine, but to work more professionally, I'd like to start using a more formal approach.

Do you think it's something I could approach her with at some point?

The approach so far is containment, water extraction, dehumidifiers, anti-microbials, manually removing mold, sanding all wood surfaces once dry, hepa vac, kilz coating of all surfaces, hepa vac again.Perfect storm:enclosed crawlspace, still air, hot water, spraying water leak for at least one and up to two weeks straight.  

If you don't have a mortgage/financial pro, I would recommend approaching a handful of investors who have been successful (for more than just 12-18 months) and asking them for a referral to their "money" guy.