Buying a lot with recorded tax liens

[Cat B.]

Looking for my first lot to purchase and would love the community's thoughts on the risks associated with this transaction. 

I found a piece of land posted for sale by owner and priced at half of its market value. 

So far the catch I see is that the city has recorded tax liens on it since 1997 since 1997 to the tune of $7k. Of that $7k, $3,4k is listed as principal, $2k as interest, there's a little bit of penalty and $1.7k shown as "Other". 

Can I buy the property for what the seller is asking, pay the city the lien balances of $7k and call the title clear? Or are there other debts, liabilities, and hassles that are likely to result from this type of buy? 

If it matters, the tax account for the lot address is under Jane Doe and the property is showing as owned by John Dow trustee of Jim Doe (these are not the real names, but you get the idea). There's only one sale recorded for the land from over 60 years ago. 

I'm about to ask the seller for more info. I appreciate any advice on what I should watch out for and expect. Thanks in advance!