@Feng Ye Insurance has become increasingly more expensive in Florida, but not to the extent you should not buy something here. They are finally fighting back against all the fraud that has gone on for decades.
You mentioned you want a 'cheaper, older home'. That statement tells me you will be getting a home that needs updates and likely will be more expensive to insure. Homes built in the 60s or older will need plumbing updates, electrical updates too. Look for galvanized pipes for anything before 1970, look for Federal Pacific, Zinsco, and other electrical panels that insurance companies stay away from. If the house is from the '80-'90s, you'll need to watch out for polybutylene plumbing, in the early 2000's, Chinese drywall. And if the roof, water heater are more than half of their life expectancy, yes, the insurance will be more expensive.
And those are just the bigger systems to worry about. The a/c is the only other big ticket item, but insurers won't give you issue with those. So if you want an older, cheap house, you have to know walking in that these will be issues you have to plan for regardless of what state you are buying in.