@Tyler Carpenter, Tyler my first rental was purchased with my LLC. What I discovered is that because you are buying it in the LLC's name you will have to finance it with a commercial loan. The issue I found is that most of the bigger banks would not lend to my LLC, not because of the lack of business credit, but rather because the purchase was not large enough that they considered it not worth their time. one bank in particular told me if the financing was not more than 1,000,000 they were not interested.
I had a lot more success with with smaller local banks because, i think, they are more interested in the local market and businesses. I did however, have to personally guarantee the first two that I purchase this way. after that I seemed to have a track record with the bank and they allowed me to obtain the loan in the company name with out the personal guarantee.(not sure if about your bank obviously)
the strategies that your mentor is recommending to you, purchase the property in your personal name and then transfer it to the LLC after closing could cause the bank to call the loan due. (they dont like that)
Finally to address your other question about LLC's, the primary reason I use a LLC is to protect my personal assets and credit. If the mortgage is in the LLC name (assuming you didn't guarantee the loan) , then if the LLC defaults then it will not affect your personal credit at all. Additionally by putting the property in the LLC helps to prevent someone from suing me personally should they get hurt on the property or something of that sort, it will not however, stop them from going after the LLC assets if you get sued personally.
I also purchased a $1Million umbrella insurance policy to protect the LLC and myself. This policy is cheap ($180 per year) and it helps protect my company if the LLC gets sued. It will also help protect me if (and only if) I have an accident while on company business and get sued because of the accident.