If the real estate is sold and deed is transferred to the buyer as in a traditional sale with a mortgage rather than deed of trust, and the Buyer should default, you would have to go through the traditional judicial foreclosure process. This can take months to years, depending on the legal representation on each side and how the original documentation is drafted.
With a deed of trust, which is not typical in Florida, a foreclosure is not a judicial process, but rather completed by a trustee, and normally only takes a few months.
Typically with owner financing one will ask for a 20% or greater down payment from the buyer, and require a percentage rate of interest above typical bank rates for the time. This is because the buyer is normally unable to obtain financing in a traditional method due to credit or other issues. Be sure to get a full picture of credit, assets, job history, etc. of the buyer(s) before entering in to any agreement of such. And if you feel uncomfortable - DON'T DO IT. As I said, it can take months to years to complete a foreclosure should the buyer default.
Please also hire an attorney to represent your interest and draft the mortgage, note and other documents needed to facilitate such a transaction.
You may also want to consider a lease option, or lease purchase. where you retain deed to the property. With this, a foreclosure proceeding would not be required, but rather an eviction which typically takes a few months.
Before you can consider any of these options, you will need to contact your co-op to see what is allowed.
I recommend seeking the legal advice of an attorney regarding all these options, as I am not an attorney and not able to give legal advice.