Cash flow and cash reserves

[Taylor Hawkins]

House I want: 

I'm in Southern California buying a 3B/2ba SFH across the street from me. It has been unoccupied for decades and needs a lot of work. At 1400sq ft I'm budgeting 100-150k for remodeling. It has a huge lot and my city permits ADU up to 800sq/ft without too much fuss which I'd eventually plan to develop and rent. mortgage 7k/mo.

Current home:

I'm house hacking a 5b/2ba SFH with a 500k loan valued at 1.4M. Mortgage 3k/mo but it's paid by my tenants.

Cash I have: 

Cashing out everything (stocks on ETF) but 401k I’ll have 700k. With 20% down and remodeling expenses I’ll deplete that to around 350k.

Cash flow:

Worst case I’ll need ~10k/mo to keep both mortgages afloat. I could likely rent my home for 5K/mo and rent a bedroom in the new house for 1k/mo.

Given the uncertainty of repairs, landlording, and the macro environment what cash reserve would you feel comfortable with for this kind of leverage?