If you can't afford flood insurance, you can't afford to own a home.

Flood insurance, although only required by lenders when a home is in a flood plain, is a must for everyone.  The cost has been between $500 and $600 when you are not in a flood plain and needs to be paid before closing, not at closing.   This is real important and I don't know why insurance agents do not offer this advice.  The base rate when you are not in a flood plain, should be the same with all agents since this is a government subsidized program.  Check with your agent, but you should have immediate coverage if paid in full before closing.  If paid at closing there is a 30 day lapse in coverage, only when you are not in a flood plain, which you want to avoid by prepaying.  If your insurance agent can't offer this immediate coverage with prepayment before closing, find another one.  

If you are in a flood plain, there should be no lapse in coverage as long as it is purchased with first ownership, even if paid at closing but double check this with your agent.  A lender will require the coverage and your rate is determined by the elevation of the house you are purchasing.  An elevation certificate can be ordered with a survey or you may be able to use the current sellers certificate.  The cost will vary depending on the BFE (Base flood elevation) compared to the lowest level measured of the home.  You can ask the current owner for information regarding their cost, but there is no guarantee that will be your cost so always check this with an insurance agent.  Know your cost upfront to reduce surprises at closing. 

My home flooded for the first time during Harvey and it was so sad to see the people that had no coverage that could have obtained insurance for a relatively low cost compared to the coverage.  ALWAYS carry flood insurance on your home, even if it is a possible teardown.