I live between Tallahassee and the state line with Georgia, in rural Gadsden County. Barndominiums are as common as rain around here. I get the pleasure of coming in and finishing them after the home owners get started. Each county in these here parts has multiple companies building pole barns. I have found that most actually do a good job of building them square and straight. no complaints there.
So, the deal is to research the particular area/counties where you want to build, and get references for the "barn builder".
I just finished one in Bay county that passed all the windload requirements, etc. We did the outside walls of that one in hardi board and batten and from the road it appears "stick built". Another project was more high end with over $40K in just interior millwork (recovered 150 year old cypress trees out of the Apalachicola River). That one has metal exterior walls and from a satelite looks like a maintenance building on the farm. So, the sky can be the limit in terms of square foot costs.
All the ones I've done in the past 7 years have used sprayfoam insulation. A word of caution... some Florida counties are now not allowing the sprayfoam to be applied to the underside of the metal roof. They are requiring sheathing under the metal, and the foam then applied to the underside of the sheathing. Sheathing is hard to put on trusses that are 10 feet apart. That causes a major retrofit., or redesigning a roof under a roof. It is "gotchas" such as that causing most barndominiums that I have been part of to cost more in the end than a stick built home. Just saying.
It takes a lot of framing material to frame up a polebarn into a residence, especially in matching up to the metal trusses and 8x8 poles. Also, retrofitting facia and soffets and gutters on a polebarn is not as easy as on a roof with trusses 24" o.c. All things to consider.
One family member went first class with a 7,000 sf Morton Building (top quality) letting Morton put in the exterior doors and windows n the corner where he planned to later build out a residence. We then built a 1500 sf home in that corner of it. Lots of ways to skin the cat.
I don't tell any of my customers not to do it, but I do tell them that in the last decade we have not finished out a livable home inside a metal building for less than what it would have cost to just build it as a conventional home. YMMV
Also, many of the reputable barn builders in my area are telling me they are booked out 5 to 6 months.
An example of a reputable barn builder is Better Built Barns in Hosford Florida.