What paper pitfalls are out there? (i.e. liens, titles, etc.)

I'm brand new to real estate and reading up on the general transactions of property purchasing & selling, but it seems that there are non-physical pitfalls such as liens, titles, and possibly others.  I only know that liens are generally taxes/debts that have not been paid on a property and the title is who owns the property, but I've heard titles can be more complicated than it sounds.  Are there other potential non-rehab/non-tenant pitfalls that result in a deal costing more money than anticipated or even the collapse of the deal itself?  I'm just trying to clear up my naivete. 

Sincerely,

The Noob - Tony