I try no to buy from wholesalers, but my opinion of wholesalers in not what the issue is here.
Buyer should be doing all the homework before purchasing any property and getting title insurance if they think they may needed.
One of the properties I got from the MLS went through a title company and a title search finding no liens. Purchased this property for $13,000 back in 2010. After we did some demo, we wanted to put plans on the city and we found a $77,000 lien. After a few phone calls title insurance paid us back the $13,000.- we paid for the house. We were not going to pay $77,000 for that lien, so we got a lawyer and he was able to remove the lien and charged us around $2,000.--
After learning this, we found another house in the MLS for $80K with a disclosed $30K lien. With some negotiations, we got the house for $60K, and repair the code enforcement issues on the house. Then went to the city and negotiated the lien paying only 10% ($3,000). Numbers worked much better now.
Liens are not always a bad thing. It may give you leverage to pay less for the property.
Disclosed or not, it is your job as a buyer to find everything you need to find to make that transaction work. Not the seller or the wholesaler. Expect the worse and be prepared.