You would need to factor in property tax and insurance increases and future repairs/cap ex. 

You have to factor in the increase in the cost of your money.

If you're comfortable with these factors and the cash flow remains strong, it could still be a great opportunity.

Can you show reserves factoring the DP and closing costs?

This could mean investing in property flips or purchasing out-of-state rentals for more stable income, but it would require letting go of the $1,350 rental income from the manufactured home.What factors should I consider for each option, and how would an experienced investor assess this situation mathematically?

Just remember to factor in that you will now have fixed monthly payments on the original three which will reduce your cash flow.

Keep in mind though that your return on equity on your 400k equity goes from 1.5% right now (assuming 500/mo positive cash flow) to getting a -3% on the remaining 200k in equity, so that is also a factor.

My opinion is that the overall direct effect of immigration policy on any given market will pale in comparison to other factors such as the economy, inflation and deregulation. 

The first is the way dividends or rent is payed is through tokens which recently have been under pressure due to their transaction cost, it's not a deal breaker but it is something that factors in when you go to turn your tokens into money.

These factors typically indicate strong rental demand and potential for property value increases.