@Scott L. I would start with the marketplace section here on BP. I would also join every FB group for investors, from local to California, and post the package there as well. Also on Loopnet, which you could do yourself. If you are looking to list the portfolio, the agent could do Loopnet and the MLS.
If you are looking for a private sale I have a few investors that I could shop it to, as well some private groups that I am a member of. Feel free to shoot me some high level particulars and I can keep you anonymous.
I have a friend here who has about 140 houses right now, who I was discussing return on equity with. When we looked at what his cashflow is currently, and then considered what he would net out of a sale post tax, he decided to keep owning the properties. His reason was the only thing he knew to do with the proceeds was to loan it back out at 12%, and he would be "behind" where he is now in cashflow.
His proceeds would have given him options up to and including PE, but he is a simple man and in his case holding was the option for now.
That may not apply to you, as a financial professional, but I thought I would share the story.
Obiously you could re-lever your portfolio to bring the ROE back up, but then you have to place those borrowed funds somewhere that nets a high enough return that the portfolio is ahead, given the drag of the interest and any transaction fees.