You already have expressed a concern about neighboring properties/companies.I'm sure a quick search of the Internet will provide you with articles/info regarding stories of people buying properties for $X, not doing sufficient EDD, and subsequently finding out that there's an environmental issue and the remediation will cost a multiple of the $X purchase price. 

The concern was the weight of a vehicle on the lawn could damage the sewer line. 

We tried offering cash for keys, but that did not work.Trying to purchase the property from a relative. but every one is concerned about the dead beat who will not budge and not move at all.  

one of my main concerns is the liens and other liabilities that you could get into when purchasing those properties.Does anyone have a check list of things to go thought.Thank you guys

My biggest concern would be the figure beside home owners insurance.  

There are also new laws concerning those who have received notice, no more "I can help you" arrangements or interfering with any foreclosure process, banks don't due lease purchase deals.

My concern is that when I get the foundation repaired , the plumbing is going to break .

BUT, if your goal is to get started and you aren't concerned with counting someone else's money, maybe you can meet with the person to see if you 2 would be a good fit to work together.  

With this in mind, is it better to say I am interested in purchasing the house and then risk be ignored if they aren't interested, or simply say I wish to speak with them concerning a matter on the  house, for example, so they would need to call to find out what the issue is, and I can remove them from future efforts if they aren't interested?

Even if a bogus claim is made concerning your period of ownership, the costs to defend your ownership and the future owners' rights may fall on you.