Does anyone know what is necessary if I want to "buy" an already leased property. If there is only 15 years left on the lease, can that lease be cancelled and a new 30 year lease replace it?

If not, do I just sign a sub-lease for the remaining years, does it need to be registered or have the owner's (of the land) approval.

The very first thing to do is to make sure the lease can be transferred. Some cannot. I don't think it would be likely that the person who owns the property will extend the lease but you never know until you talk to him/her.

My comments are as follow:

Does anyone know what is necessary if I want to "buy" an already leased property. If there is only 15 years left on the lease, can that lease be cancelled and a new 30 year lease replace it? You would need the lessor to cancel the old lease and give you an extended lease.

If not, do I just sign a sub-lease for the remaining years, does it need to be registered or have the owner's (of the land) approval. Again, agreement from the owner is necessary. A lease of a period of more than 3 years is required to be registered with the authority.

If you buy the leased property then you are obliged to honour the lease to the tenant unless you agree otherwise. If you mean that you are buying the lease and not the building, then you would need to have it transferred, if possible, or a new lease written up. You should know a lot about that situation long before you part with any cash.

Does anyone know what is necessary if I want to "buy" an already leased property. If there is only 15 years left on the lease, can that lease be cancelled and a new 30 year lease replace it?

If not, do I just sign a sub-lease for the remaining years, does it need to be registered or have the owner's (of the land) approval.

Who is it leased to? Yourself or someone else? Are both parties happy to terminate the lease early? If not, forget it. A contract is a contract.

If you sub-let, be advised that any lease longer than 3 years needs to be registered.

Whether the sub-let needs the owner's approval will depend upon the terms of the head lease, but most likely yes it will.

Finally, if you want to buy it the owner will need to be consulted at some point.