Sewer video question

We are in the process of buying our first park and we are confused about how to proceed with the sewer check. Any advice and opinions would be helpful. Here’s the situation:

It is a small park, just a dozen homes. There are no park owned buildings. The township requires a lateral test to be done (every few years) when the park is sold or refinanced. They have record of a recent lateral test (so they aren’t requiring us to do one with this sale, although they are requiring us to do a dye test on three homes) and says it passed inspection and everything is ok. I was told that they put the camera down the man hole, the park has one main line off the city’s, and they were only able to check the first couple trailers. He said it is impossible to check out the rest of park because each trailer has it’s own system. If we were to move in another home to the park they would then check that system. There are no vacant lots, but there is one vacant home that the park is currently getting possession of.

OK, so I guess our question is, do we need to do further testing of the sewer? Do we want to go into each trailer and check it’s sewer system?