Properties here are pretty expensive and want to know if it still possible to be successful here.

That number is not realistic.To refinance the property and get cash out it needs to be completed as in everything done and inhabitable, unless you do a short term expensive hard money loan and then refinance later and pay the costs twice. 

The second question that I get from owners is "Would you be willing to lower that"?

In either scenario, you're most likely going to refinance if/when rates comes down so you may as well take the lower rate.

My plan is to immediately move the three lower units to $1400, then in 6mos move to $1450, then a year from now, bump them to $1500 (leaving the one at $1550).

Some work that comes to my mind is:1) Managing tenants to get rent paid2) Diagnosing a repair issue and getting the right team to make the fix3) Fielding messages from prospective tenants on advertised rentals4) This list goes on...I've found a company that automates rent collection and income/expense tracking for free, but I'd like to replace my property management portal altogether and feel I'm only half way there (certainly a tenant facing chat bot would close the gap).

I agree with Shawn, while expensive in some areas, it is not saturated for LTRs in Central Florida given the migration data.

I would be curious to see what a more expensive and more permanent home does for the ability to lease that land back to occupants.Would you be building the tiny homes and selling them or keeping them as a rental?

You can't force them to make repairs or lower the price.

Basically financing of 10% is always assumed in our calculations/expenses and if I'm the one who puts up the money I make that 10%.