When/if you sell, as long as you qualify on both fronts, you will be able to take a portion of the profit tax free and use the remaining in a 1031 to purchase more investment real estate.Your accountant will have set up a depreciation table on the investment portion and have allocated the % of the whole that is used as investment.  

Where it's such a short time frame, I'd say take the money off the table and get going on that 203k rehab, which will probably accelerate your equity much faster than $140/month.$140/month * 12 months / $30,000 equity = 5.6% return on equity per year before depreciation, loan pay down, and an interest deduction.

What does he bring to the table? 

Charleston has a high water table and a lot of sandy soil. 

You have the possibility of unfinished basements that can be finished adding bathrooms and bedrooms to increase value, but anything exterior like you said wouldn't typically be on the table.

Leave your offer on the table.

SF market is hot and with multiple offers on the table for units, sellers are not interested in 3.5% down when they are getting over asking, 20% down or all cash offers. 

Put in a partial french drain.  

My question is has anyone closed with a bank with less money brought to the table "besides" the 20% down.

The loan does not show up on your credit report.You can close immediately...kitchen table, if you call a traveling notary.