Registering out-of-state LLC as a foreign entity

[Gary Parilis]

I have an LLC formed in PA and I intend to invest in other states. In particular, I'm looking at properties in Tennessee and may be making a purchase soon. I've been reading that it's necessary to register as a "foreign" entity (that just means out of state) to transact business there. This seems to be true in most states. I have also read that it is possible to do business without registering (and my agent says his closing office indicates its not necessary), but if I don't, the following applies:

"If your LLC transacts business in Tennessee without a Certificate of Authority, it cannot bring a lawsuit in the state. Moreover, if your LLC transacts or conducts business in Tennessee without authority, it is liable for fines, and no Certificate of Authority will be accepted until the fines are paid. However, not having a valid Certificate of Authority does not invalidate any of your LLC’s contracts or stop your LLC from defending a lawsuit in the state."

Does anyone have experience with this to share?

Also, among the requirements to register is: "The street address, including zip code, of its registered office in Tennessee, the county in which the office is located, and the name of its registered agent at that office".  

Do I need to hire a registered agent? 

Thanks.