Cost effective termite prevention strategy?

[Bienes Raices]

I'm trying to find a happy medium. This is for a rental house that doesn't have termites--yet. The termite bonds with annual fees seem like kind of a ripoff, and I don't know if the 50% rule accounts for them or not. Someone on another forum suggested to DIY with Termidor, but I've read that you can't even get termidor on your own, and then I wonder if there would be issues with doing it correctly, as well as liability.

What do people on here do, get a one time preventative treatment, or wait until there's visible evidence of termites before doing any treatments?

The houses in this area are mostly block construction with slab on grade foundation. It seems like I could do a visual inspection on my own without paying for one. I assume that all they do is look at the soil and structure around the perimeter of the house, at the trusses, soffits & fascia? It seems a waste to pay for annual inspections on a house where you can't get under the foundation anyway.

Thanks!