While you technically might be able to flat tow a Mustang, Ford highly recommends that you don’t for numerous reasons. Depending on the model year, you can damage the transmission and void the warranty. Mustangs out of warranty are also more susceptible to damage when flat towed, and you wouldn’t want to damage your ride when you can avoid it.
The only Ford-approved way to tow a Mustang is with a flatbed trailer. These trailers often run between $1,000 and $3,000 on the used market, but the protection they provide is worth their weight in gold.