When investing through an LLC, if you invest outside your state if incorpration, do you need to file a DBA (Doing Business as) or anything similar in the state you want to invest in? Or is it better to start another LLC in the new state?
I think you do need to file the dba with each state's corporation commission or equivalent. I think it's not necessary to file with each county. You definitely do not need to start a new LLC. Lots more paperwork that's probably unnecessary and lots of extra fees, etc. An LLC can operate in multiple states just like a corporation can but you may need to file the dba to be safe. It's cheap.
Also, you may need to pay state taxes in the states you operate, even if they are different from the one in which you originated the LLC. This becomes a mess and often times both states--the one where you did the business, and the one where your LLC was originated--will try and claim rights to your earnings.
You'll also need to comply with all local and state laws where you are investing--can't use lenient laws in your home state where you originated the LLC to shield you from lawsuits or problems in the state where you are investing, e.g. A Virginia (landlord-friendly state) LLC invests in property in Massachusetts (landlord-unfriendly state). At best, problems in your Massachusetts properties will fall under Mass law and at worst you will have to comply with both states' laws, yielding to whichever is more restrictive.