It might make the most sense to just sell your primary residence and use it as 40% to 50% down payment on your future home. 

It is already renovated, tenant-occupied (or ready for tenants), and generating income from day one.

I like the idea of STR as it seems like it can generate significantly more income than LTR and would allow me to block out dates if I have friends or family come visit.

My property generate 4100 per month and it is a 2 family.

Trading off current cashflow for principal payoff in the future?

In the future, either get your Real Estate License so you have access to the MLS, or make friends with a realtor so they can get you comps to get an ARV.  

For the future, remove other door knobs that don't need to be keyed unless you have the keys and strengthen the lease to address lock outs. 

Now that I am in position, I would like to place a mobile home to generate some passive income, but I don't want to use my savings for the down payment.

I think over the foreseeable future we will see this continue due to rising prices in those markets like California and New York.

Or we gradually perform high-quality updates for a live-in flip, then roll the equity into a new home.Regarding rental income, we aim to boost income, lower our effective tax rate by generating more low tax-drag income with rental income (since there’s not much we can do to lower out W2 tax bills) and have retirement cash flow.To compare the financial impact over 10-20 years, we want to analyze renting versus flipping.