My accountant has me form a different LLC for each investment property I own. It is so much easier to keep the expenses/income straight when you file them with the respective property. No comingling of funds, either. I'm in NJ, fyi. Each LLC has the corresponding address attached to it. It's simple and it doesn't cost much to form an LLC either.
I am not an attorney and my answer to you is not legal advice. However, and in my opinion, you do not need any LLCs at all. I am a real estate investor and do not create LLCs for my investment properties. Yet, many people swear by LLCs and even some of my fellow real estate investor friends create a new LLC for each new piece of investment property. Feel free to contact me directly to discuss these matters. I am more than happy to share with you my real estate investment experiences. Best, Mark Palace
Really - this is a question for your accountant. Your state laws will determine what is financially feasible - depending on the tax base for an LLC or how it affects your particular tax bracket (personal).
It my humble opinion, having separate LLCs for each investment property makes only sense if you co-own the properties with different people. If you are the sole owner or all owners are the same for all the properties, having one LLC for all of the investment properties seems to be sufficient to me. Whether you need to create an LLC at all is a different question and the answer depends on the benefits that you get from owning as an LLC. As Mark has already pointed out, an attorney who specializes in that field would be the right person to consult with.