I hire them to do simple due diligence up front. usually 3k to 10k.. to determine if the plan is feasable from a building perspective as for market perspective I rely on my own expertise to understand what works monetarily.3.

Given the nature of your question I am guessing that you have some friends or acquaintances who wish to pool capital to invest together in a syndication opportunity and they're relying on your expertise in some fashion to decide if the deal is a good one. 

You invest your IRA in real estate because you believe you can better protect and grow the IRA with real estate than other investments.The structure you have been introduced to is a "checkbook IRA", where the IRA owns an LLC that you can control.  

The best thing you can do to protect yourself is to have the basement tested for mold by a company that does only mold testing and not an abatement company.At the same time, you can send your tenant a letter warning them that they will be liable for mold testing if no harmful mold is found and you will pay for testing if any harmful mold is found.The very next thing we do is; send your tenant a certified letter telling them that if they suspect their health is at risk for any reason that relates to their rental unit then your tenant should not reside in your unit for one more minute and should move to a place they feel is safe because you will not assume liability for exacerbating their health issues, if any health issue in regards to mold exists.At this stage, all communications must be in writing and well-thought before communicating.Your situation has happened to us several times and we had a tenant who lived in a brand new unit for only 10 days and he told us he was vomiting and had nose bleeds that resulted from mold.

Should I get liability insurance in order to protect myself if any incident would occur.

If you have friends or relatives in other areas, leverage their expertise of the area and they can be your boots on the ground (don't abuse their time of course) and you can reward them financially if a great deal comes along!

Aside from the risk of the due on sale clause, for any property that does not have its mortgage under the LLC, the asset protection might be questionable as this might be a form of co-mingling.

The heloc is my primary source of investing money so i am trying to protect it from getting frozen.

PS - I'm somewhat protective of the commercial lender that I use but if you want to PM me I'll share him there.  

I understand that with the passing of the latest Housing Stability and Tenant Protection Act in 2019 in NY, it really eliminated the up-side of stabilize building.