It will get down to the definition of carrying on a business as compared to a hobby. If it is your only source of income and is repetitive, it leans one way, if your main source of income is a full time PAYG job then it may lean the other way and be treated as wylie suggests.
To get away from the CGT issue, others buy as a PPOR, live in it as they renovate, then sell. Having done it once, not what I would want to live through again with young kids (at the time) but many do.
Manufactured growth like this can be an excellent way to increase your wealth.