A permanent address. It can be a mail service or a relative or a friend but you need someone watching your mail. A trusted relative or friend is best. I gave my sister power of attorney and it came into play several times during the years of cruising - mostly for financial transactions.

Boat liability insurance. Hull insurance is harder to get and often has requirements that cruisers can't meet.

A thorough knowledge of your boat and it's systems. When you are away from the U.S. marine trades finding qualified repair services is far more difficult than many would expect. Unqualified service charlatans are plentiful. Self reliance is your best bet.

A good set of tools and the knowledge to use them.

A good supply of service expendables - oil and fuel filters, oil, sail repair thread and other sail repair supplies, etc. At least two sets of spare belts, more is better. When you use one start looking for a replacement.

Service manuals for engine, transmission and any other complex mechanical equipment you have aboard.

You do not need an immunization record. I have never been asked for one even though many sources say you need it.