Suggestions Would be Helpful......Which Door to Open up?

[Sam Mathew]

Hello Bigger Pockets Team Members,

Approximately three years ago, I started investing in real estate as a side hobby.  I started buying small SFHs ($75-100k homes) and renting them out, and here and there I would also buy and flip.  I started with a modest amount but using 1031 exchange and some other investments, I now have approx $500k available to invest.  Of course this crazy real estate run up helped quick a bit with it.  

Now, I am experienced with small SFH but would like to take a larger step (although more risk adverse in my mid 40s).  I was hoping to seek input/guidance from experienced people.  Does any of the following seem more attractive and also less time consuming (as I still work a full-time job in IT):

Door #1) Continue building slowly but surely with SFHs?
Door #2) Look to buy a first multi-family apartment unit with 8-12 units?
Door #3) Look to buy a first commerical office suite or similar?
or Door #4) Something else unique and interesting with real estate?

I feel somewhat odd posting this request for guidance, but I felt that maybe the Bigger Pockets team members would likely be much wiser than asking my family members or friends who have not much experience with real estate.  Please let me know your thoughts if you are open to sharing.  Thank you and very appreciated.

Sam