Right now I have ~$13k in cash/savings based on a total monthly expenditures of ~$3,500 (personal expenses + automatic investments + rental property outflows), so it seems to be just under 4 months right now of gross expenses.
I'd feel more comfortable with 6 months, so probably $21k as a loose target. This is probably way more than I need, but it's just less stressful to have more than I need.
I looked into setting up a HELOC, but since I own my rental outright, it got complicated with certain banks denying me since they only offer HELOCs on owner-occupied, or only if I had a checking/savings account with them, etc, and then I quit looking, lol.
I think in theory, it would work best to have 3 months on hand in cash, and then a HELOC at a floating rate for up to 1 yr of expenses since HELOC rates are much lower than credit cards, personal line of credit, etc.