A survey commissioned by and for the owner is no insurance for you. The only way to do this is to get a qualified person (or business) to carry out a full survey to your specification. They will need to know intended use as a part of that and if off-shore in this yacht is your intention they need to know that.
For a steel yacht of that age and your intended use I'd go for a full rig inspection and report, a hull/deck/superstructure survey and a mechanical and systems survey (engine, gearbox/drive, electrical, electronics). It will be pricey, but you have the reassurance and the surveyo