Buying a 150/152 to build time is a gamble. I know two people that did this.
One bought it as soon as he got his private, did his instrument, and time building for commercial + some time building after commercial, and 9 months to a year after he sold it, and said he pretty much broke even with repairs because he was able to sell it for a little more than he bought it for.
The other person I know that did this, got really screwed. Ended up having to replace the radio within the first month of owning it, and then in the middle of the time building needed to get the engine overhauled, and it was only about half-way to TBO. And now he's trying to sell it.