Almost every remodel budget that blows up in Florida blows up in the same three places, and none of them are the part people worry about when they start calling contractors.
The first is allowances. A bid that says "tile allowance: $4 per square foot" is not a price, it's a placeholder, and placeholders are where lump-sum bids hide their softness. Ask for the estimate itemized, then go look at what $4 tile actually is before you sign. If the number you would really choose is $9, that difference belongs in the budget now, not in an awkward phone call in week three.
The second is what's behind the walls, and it is the reason we look at a property in person before quoting. In Tampa's older bungalows it tends to be wiring, galvanized supply lines, and floor framing that has already been patched by someone else. In block homes it's plumbing that can't be moved cheaply because it's cast into the slab. In anything older than the 1990s, opening a wall can also mean bringing that circuit up to current code. Hold ten to fifteen percent back for this and treat it like insurance rather than spending money.
The third is changes. Mid-job changes aren't a problem in themselves — people see the space take shape and have better ideas. The problem is changes that get made verbally and priced afterwards. Every change on our jobs gets written and priced while it's still a decision, which keeps the final invoice from being a surprise.
One more honest note about Florida: if your roof is more than about fifteen years old and you're already spending money on the interior, price the roof at the same time. Doing it while the crew and the equipment are already on your property is meaningfully cheaper than doing it in two years as an emergency, and your insurer will care about it long before your kitchen.