With any older boat you have to understand that the transom and stringers will have some rot, the full extent is not known unless you tear it apart. You can either spend 3-400 on a survey or read up on sounding a hull for rot. Lots of info and you tube videos on the net. Generally I have not heard bad things about Sangster hulls, usually you hear how they were built like tanks, lots of fiber glass used in them. Look at the hull and check for blisters on the bottom, check out the floor for soft spots. I am guessing it has a mercruiser engine? The age of manifolds and risers is important, I generally go with 4 years on manifolds and 2 on risers but the more use the longer they last. My old searay had 8 years on manifolds and 4 on risers but I used the boat a lot. Post a pic for us.
I just bought a 1984 Hourston and even thought I sounded the transom and strings. I know that I will find rot when I pull the engine next month, but I enjoy a good project.