Note: finding bank to finance deal seem to be more difficult than I was lead to believe.

There are so many IRS restrictions and prohibited transactions within a Solo 401K that it makes it difficult to navigate.

It will actually be more difficult for your agent to procure a buyer off market - so the work actually increases. 

Basic stuff like LTV, NOI, cap rate, etc...There are a few report types missing and you can't split expenses yet.

Total time spent throughout the year may be significant, depending on the number of properties and amount of activities, but year end is no more difficult than any other time period they're doing. 

What you want is an agent with experience who knows how to negotiate, watch your back, navigate difficult situations, understand contracts and law, provides an objective cross-check, etc.

If one or more units are vacant, the remaining units often don’t provide enough cash flow to cover expenses, making it harder to meet operating costs.Maintenance costs: A fourplex comes with four times the appliances, plumbing, HVAC systems, and other components to maintain, leading to significantly higher repair and maintenance expenses than single-family homes.If you want to see the detailed calculation, read this BP blog - More Units Doesn’t Mean More Money—Why a Single-Family Home Can Beat a Fourplex.Resale value: Multi-family properties have a limited buyer pool—mainly investors—who base their offers on CAP rates.

Getting needed coaching from professionals who had made deals was difficult and the two deals I invested in were very poorly managed from the beginning. 

Going direct to client is the holy grail but is more difficult.

Its also the right sort of thing to do to try and help someone navigate a difficult time.