Equity question for long term play.

Hey everyone. I’m new here and wanted some opinions of others. I’ll make this as concise as possible while providing enough information. Question is for a close friend.

Owns a SFR on the west coast 3.875 interest rate. Cashflows 520 a month. ~225k equity. Low ROE

Duplex in Midwest 4.785 interest rate. Cashflows 715 cashflow. ~100k at about 8.5 ROE

Has about 300k in reserves (interest bearing accounts) 4-8%

good job making between 100-500k depending on the year, economy, life etc.

30 no wife and kids yet. and plan on keeping job for long as possible.

What would you guys do in his shoes? 1031 SFR and use cash to buy commercial?

Buy small multi? SFR? Flips? Put it in stock market and wait? Keep saving for next downturn?

Thanks for opinions and input.