I allocate a certain percentage to each asset class and re-balance them once a year.

RUBS is (if I remember correctly) Residential Utility Billing System, it's basically a scheme for figuring out how much of the utility bills should be allocated to each apartment unit, based on factors like unit size, occupancy, etc.

You can just allocate the equipment costs to your rentals, no need to set up a separate entity.

LLCs with strong operating agreements specifying who the managing members are and who the non-managing members are second in popularity.On the tax entity side, it's generally preferable to have a syndication taxed as a partnership.Partnerships are very flexible with income and loss allocations as long as those allocations have substantial economic effect. 

Some do monthly, quarterly and yearly and some on refi or exit.Depreciation allocations are up to the syndicator and if shared are generally on a pari passu basis.

The HOA fees are definitely going to kill your cash flow potential each month and you will need to analyze the HOA's viability and their reserve account and projected capex allocations for the future.

I would recommend doing some more research of the allocation of the average retirees retirement accounts.

I allocated the whole morning of Friday just working on the business.

Looking at a portfolio from a holistic point of view, The ideal allocation I like is 50% real estate, 30% your own business/investing in private businesses, and 20% stocks.That said, without leverage, the S&P 500 will generally out perform the real estate market in the LA and Atlanta as your can see from my chart below.I also agree with @ J Scott that you must specialize and focus, rather than diversify.

If you are still worried after analyzing these factors, you need to focus on asset allocation.