Foundation crack on (quasi-permitted) addition

[Mike Warder]

I'm looking at a short sale house that has a permit for a glass rear porch built in 2002. Listing agent says permits were not gotten for subsequent updates to that porch and the foundation on the porch now has a crack. The quote to fix the foundation issue was $5,500 to install 5 helical piers and get the permits. This would be a buy and hold for me. 

1) is this foundation quote reasonable?

2) was a permit likely required for walling up the 200 sf porch?

3) would getting the city (goose creek, sc) to approve permits on the foundation work open us up to unwanted scrutiny regarding the updates to the porch? Is getting the proper permits worth the likely expenses we would incur for the inspection, any remediation?

4) what other problems/solutions should I be thinking about?