I know that I would have to pay UBIT if I BORROWED to purchase a property in my SD 401k using a participating loan.

I would further recommend that you both partner in an entity like a LLC with your LLC as the 50% member and the other party can participate as an individual if he/he wishes.

. - What are the liquidity options for investors participating in a syndicate?

That type of sizable deduction could help whittle down a large tax bill.https://www.investopedia.com/articles/07/oil-tax-break.aspIf anyone has experience participating in this type of investment or knows well-known and respected operators in this space that put together limited partnerships and private placements, please share that info here. 

I also participate in my office weekly sales meeting and hear about deals pre-market and it has expanded my connections with lenders, sub-contractors and other agents, etc.

That would probably be a private person - someone you know, or get to know, who will participate in the deal.

I checked out DIG and it looks like you have to have a membership to participate.

I already participate a generous amount of my paycheck in a 401k program, so I am partly looking to diversify.

I have been a lurker in the forums for the past year but recently realized that I should start participating/contributing.

Here are some specific action items:-build out your profile on BP, I want to see a picture of you, know what you do and what your goals are-be helpful on BP, start trying to answer/participate in posts where you have some value-start reaching out to people on BP specifically, with small, specific asks-go to a few networking events every month and plan on talking to many people...it takes 5 + bad conversations to find 1 good one-go to 2-3 conferences per year and be very purposeful there in your intentions, don't just go to sessions and stay quiet, be intereactiveI probably should have started with this, but what is your goal in connecting with these people?