If the losses from your rental property exceed the capital gains from the stock sale, you may be able to use the excess losses to offset other types of income, such as W-2 income, subject to certain limitations.W-2 Income: Generally, passive losses can only be used to offset passive income, unless you qualify as a "real estate professional" or if you materially participate in the rental activity.

Even if you had a family member as a non participating member, that would satisfy the legal requirements needed to get the fully protection of the LLC in regards to tax  and bankruptcy laws.

Dozens of tax court cases on this.STRs could work if you have the time to participate properly and manage

A lot of participants last year were new investors but some had great backgrounds in real estate such as construction, real estate licenses, marketing, etc.  

We do not have the capital ourselves to do this but we have a few very close friends and relatives who would like to participate in funding such a purchase.

I'd start with your own network to find out if anyone wants to participate in an "opportunity".

Is your sister going to be an active participant in any of it?

All you have to do this materially participate in your rental properties.

Move and feel out the environment by participating in the arena you're interested in not as a bystander

This means that you participate here and get involved in conversations and keep to the forum rules.