The City of Sarasota zoning code says that if two lots, or portions of lots, having continuous frontage (i.e., street frontage) are conveyed to the same person (after January 10, 1974) and one or both of the parcels is non-conforming in respect to lot width or area, they will thereafter be treated as a single parcel.
The consequence is that when a person who owns a home decides that it would be a good investment to also buy the house next door, not knowing that the width or lot area of one or both of the lots fails to meet current zoning requirements, the two lots will thereby become one lot, and, assuming they are zoned for single-family use, the unified lot can thereafter host only one house, not two. Obviously, the two existing houses will still be grandfathered, but neither one can be enlarged, or demolished and re-built without demolishing the other house.
This result can be avoided simply by taking title to the second lot in a slightly different name than the first. Only where there is an absolute identity of grantees is there a problem.
If you run into this problem after-the-fact, there still may be a cure. You might consider borrowing some land from the conforming lot, although, unfortunately, the conforming lot rarely has any extra land to spare. As a last resort, the City Board of Adjustment has authority to grant variances. However, a variance is never a sure thing, so the best policy is to take precautions to avoid the situation in the first instance.