Can I lodge a private caveat against the debtor’s property as collateral to my debts?
No, you can not.
Caveat is not a form of security.
Caveat, is a formal notice requesting the court or officer to refrain from taking some specified action without giving prior notice to the person lodging the caveat.
If you want to lodge a private caveat against debtor’s property, you must have the caveatable interest.
Caveatable interest, according to S 323(1)(a) National Land Code 1965, is either you are claiming title to the property in question, or a registrable interest in property, or you are claiming beneficially entitlement on the property.
The debtor’s owing money to you does not give rise to any right of you on his property.