CIS or not?

Imagine an individual gets a £500,000 bonus and he/she buys a house and "does it up"

if his/her intention at the time of purchase is to sell it as soon as its been done up, he is a proerty developer trader and obliged to register for CIS so he can pay the builders

if his/her intention at the time of purchase is to rent it out as soon as its been done up, he is a property investor and not obliged to register for CIS

the building work in either case could be identical

my question is:

"Is the only thing that matters here with regard to registering for CIS is the intention of the developer/investor?"