Maybe you think I am biased but I would get a lawyer to do the due diligence. A notary's job is to make the akta. A notary only makes money if the sale/lease goes through so they may not be the best ones to ask.
Unfortunately many people run into problems because they make the assumption that everything will be fine because they used a notary to make an agreement, whether it is a lease, pre-nup or any other type of agreement.
And this is partly true in my experience. A good notary will do the due diligence. The guy I used for example did all the leg work for my land (which was a lot). The guy selling me the land was actually the son of the guy who's name was on the title who recently passed away and the land was actually in the will to three different people (all the brothers). It was a mess.
Through due diligence, my notary was able to determine all this and did the legal legwork to merge all the names into one land title so the transaction could be processed correctly. He also organized BPN to come out and determine the exact size of the land that matched the certificate and even confirmed if my access road was public or private with the appropriate authorities.
but yes, the large majority of cheap notarys out there won't even go out to see your land/property and just do whatever it takes to get the deal through as fast as possible so they can collect their rupiah.