I didn't do the proper research and found out last week I need flood insurance.

That is why you need a good Title Insurance Company who preferably is also the Underwriter. 

Specifically the course Brent Daniels offers named TTP (talk to people).

He is now selling the property and the new buyer says she cannot find an insurance company that will issue her a policy because it doesn't have central heat/air.

@Ryan SummersThere are several considerations that can go into the analysis of whether you need an LLC or whether a large insurance policy will suffice.

Handling Maintenance requests and emergencies, Handling tenant disputes, Ensuring the tenants are properly insured (if you require them to), Marketing the property, Screening applicants, Handling the security deposit return, and a whole lot more. 

They are offering a 12-15 month 0% APR Credit Business lines, isn’t hard money usually a higher interest rate?

Find a local lender (probably a credit union as they love these) that offers 2nd mortgages - sometimes called Jr mortgages, HE-loans, or closed-end seconds.

2) Define what a "cash" offer is?

Any companies or websites that offer this forms that you have used before?