Without thought I've kind of just followed the rule of thumb of capex being estimated at 10% of rent; it seems like that input might play a large part in all of my negative cash flow deals I've analyzed.Instead of estimating capex at 10% of rents, do you think it would be reasonable to back into capex by dividing $20k (a little more conservative than $16,000) by 360 months to get a monthly allocation towards capex?

If I were you I would make a plan on how to allocate the monies.

We obtained estimates from licensed professionals to compare before starting, allocating HELOC funds to things we had to hire out.

I self manage my single family rentals because it's saves cost, it's good for my personal brand, and gives me opportunity to convert tenants into sales clients.A professional management company manages my multi-families because they have better systems and I need to allocate my time to higher $$ per hour tasks.  

If not, how much rehab did you allocate for this property?

The reality is very few MF had positive initial cash flow when properly allocating for small unit count expenses before the recent rate increases.  

Personal finances set aside through the year and allocating my commission from the transaction.

If it isn't, allocate accordingly.

One potential way to get around it is for a portfolio blanket loan bundling up a bunch of properties, for those the minimum allocated loan amount can drop to around $50k for some DSCR lenders

Every time i make a payment to either I apply it, can see where I am at total with the budget and how much i'm allocating to each