@Kiran ShilamkarWith the amount of seed capital you have, you could allocate some to SFRs to start (maybe 1-2), while learning about syndication by networking on/off forum and in-person in REI meetings on investing in commercial deals, as suggested by some already. 

When a MHP is purchased and a cost segregation study is performed, a large portion of the value of the property is allocated to "land improvements" which qualify for bonus depreciation.

I want to make sure we have X allocated to categories like:- RE properties (maintenance, improvements, etc.)- Personal savings (529, index funds, etc.)- Monthly fixed personal expenses (utilities, groceries, etc.)- Fun/non-necessities (tickets for events, dining out, etc.)Have you found a good system for this? 

If you allocate enough for maintenance/cap ex, you would be the first newly that I am aware of to have done soRecognize there is a poor relation between initial cash flow and actual cash flow over a long hold.  

If this tenant has been paying for ten years, maybe just allocate some of the vacancy reserve for this and move on. 

I will provide my opinion to your questions as it applies to San Diego:1) the high LTV increase the negative cash flow that is present even at 80% LTV when properly allocating for all expenses. 2) in general, all high LTV residential purchases have negative cash flow when properly allocating for expenses. 3) adding an ADU in most San Diego markets adds less value that the cost of the ADU addition.  

I have a lot of experience in finance but not RE and I'm wondering if this degree of scale (debts>capital base) constitutes "leverage" (I don't think it does if my DSCR is meaningfully positive... maybe if I'm allocated to a single market I introduce black swans, I dunno).Having read the BRRRR book I didn't really see much on how to protect against random downside scenarios when port gets huge.

Equities don't even come close.Having said that - it is good to diversify and we are taking steps to increase our allocation to equities, but not by shrinking our portfolio!

versus severely negative  It goes further because $30K at 96.5% LTV FHA would purchase a $857K property versus OOS at 80% LTV $30K would allow purchasing a $150K RE (no allocation for closing costs or reserves in either case). 

There are other reasonable methods of prorating, such as square footage.Not sure what your tax situation is, but it's possible that on your 2018 tax return you may not get any benefit from property taxes allocated to your personal residence (Schedule A) since the standard deduction for married filing jointly is is $24,000 in 2018, so it may be especially prudent for you to seek professional advice on how to reasonably as much as possible of your expenses to your Schedule E.