Are there any good tips on how to better estimate reserve costs for new apartments?

Some are not due to HOA reserves and restrictions.  

Make sure you have enough of a reserve to account for unexpected expenses such as vacancy and major repairs.

If you have an understanding of real estate and think you can get better results growing your retirement savings in that asset class, then a self-directed IRA or Solo 401(k) is a means to do that.All investments are made in the name of the plan, all expenses come from the plan, and all return accrues to the plan.There are several different plan types and service models available.  

Their customer service/responsiveness during setup was a little lacking, but it's been smooth sailing since.

That does not include debt service, but does include taxes, insurance, advertising, lost rent to to vacancy or non-payment, legal expenses, accounting expenses, capital expenses (roofs, furnaces, etc), and property management.   

goal  = build portfolio = option Bgoal = 80% or better equity = option Aas you mentioned, the cash flow is higher, not lower, by choosing option B with the savings reinvestedoption A seems to trump option B (but I personally would do option B and maintain the proper reserves)

Do you recommend buying these lists from lead services that provide the addresses for absentees, etc?

If you're looking for stuff to renovate, you should be looking for 15-30k range per unit (upper limit reserved for very large apartments with very good bones, off street parking etc.)Joe

Another weirdness that you may or may not face...many of the homes were continually having big wet spots appear in/on the slabs, hundreds of people, were calling leak detection services, thinking an underground plumbing leak was causing these mystery wet spots.