Currently working full-time as a Senior Engineering Member of an engineering services company in Downers Grove, IL, and looking to get into REI on the side.

Welcome to Biggerpockets @Intisar Hasaan Check out the Marketplace, you'll find lots of listings from lenders offering their loans and services. 

I am a W-2 employee with a 401K plan with my employer.What I am reading, if I were to attempt the SOLO-K, first I would have to show (prove) earned income of some business activity.  

Either unit 3 will have to use a Laundromat until your tenant in unit 1 leaves, or you'll have to agree on some sort of compensation for the service (not needing to share) that you're taking away.If the tenant was told when they moved in that the laundry would be shared, tell them you're glad they got to enjoy sole use of it for so long and get over it (nicely). 

Keeping your funnel active is the key.

Hi @Andrew Orr, depending on your goals of taking an active or passive role with your real estate investments, if you're an accredited investor you might consider investment into DSTs.

I am active duty U.S.

because I have never used an online background check service like smart move I assumed that the process online would be virtually identical to the paper process that typical tenant would go through when renting any property.

 @Sam Tijerina first off, I want to thank you for your service to this country.  

if you ever needed, this resource was recommended by a contact of mine:nationwideeviction dut comFull disclosure: I do not work for them, provide any related services,  and I have never personally hired them.