New investor looking to join LLC with coworkers

[Dan Towle]

I know very little about rental properties, but I am a homeowner in the Midwest so I know just about as much as anyone else has has bought a home and done a little rehab. 3 coworkers have formed an LLC and have purchased 2 rental properties in the past two years, both are renting to families. I believe the mortgages are $95K and $120K and rent for $950 and $900 respectively. Looking at the equity of the property I could probably pitch in around $15K and own about 20% of the company. They are looking to add another and without enough money for a downpayment I told them I would be willing to become a partner and provide the additional capital. What I'm really looking for is a way to build a solid retirement plan and create a supplemental income. My wife plans to stay at home and raise the kids.

I know this isn't a get rich quick scheme, and I know there are some pitfalls of going into business with coworkers, but I basically just need advice on how to approach this and what questions I should be asking. I should also mention that two of the coworkers just moved to a neighboring state. While they still own part of the company they aren't going to be able to help with any of the upkeep. Also they are looking at purchasing rentals in that state which I would not be able to help with. So hopefully the labor would even out in the long run. 

Thanks in advance for all your help!