@Matt Liu
First of all I'm not a lawyer and have no special expertise in this subject. I am only repeating what I heard in a public presentation and in private consultations with real estate attorneys, and I may have some of the details wrong as well. I am not even advocating this approach, only offering it up as food for thought, and I leave the due diligence to you.
Two lawyers who I heard speak recommended titling each property in a separate trust and making the beneficiary of these trusts an LLC which has you as the member.
By the way, as a preface, more than two lawyers specializing in real estate investing and liability protection that I have consulted have insisted that trusts offer no liability protection whatsoever. I have heard contradictory claims from one trust attorney and the general public, but I trust these guys more. The opinion that trusts offer no liability protection is why the beneficiary of the trust should be your LLC rather than you personally.
I will give an example to make it clear(er).... at the risk of carrying on too long and boring everybody.
Let's say you had 10 properties owned by "property1 trust", "property2 trust", etc. The beneficiary of the first 5 trusts could be Numero Uno LLC and the beneficiary of the second 5 trusts would be Numero Dos LLC. So now you could have two credit cards for all those properties instead of 10. One of those credit cards would be in the name of Numero Uno LLC and the other in the name of Numero Dos LLC.
Now the paper boy trips and falls on property1 and sues the owner of property1, which is the property1 trust. The beneficiaries of all your trusts are listed on a secret document called the Schedule of Beneficiaries. Since the Schedule of Beneficiaries is not publicly recorded there is nothing to prevent an unscrupulous landlord from changing the listed beneficiaries of the property2 through property5 trusts from Numero Uno LLC to Numero Dos LLC and backdating the document to before the accident. It is perfectly legal for the trustee (you) to change the schedule of beneficiaries at any time, but backdating it is the squirrely part. So now when you go to court they subpoena the Schedule of Beneficiaries and it will show Numero Uno LLC. Then they may subpoena the list of assets of Numero Uno LLC and that (updated) list shows only the property1 trust, since all of your other trusts and properties are now owned by Numero Dos LLC and are therefore protected from this lawsuit.
I have been told more than once that in practice, when the opposing lawyer sees how the property is titled they won't take the case because they know that their odds of winning a big payoff are small.
The legal fees for setting up the 10 trusts shouldn't be much more than for 1 trust because it's the same document with only the property addresses and dates changed. Once you register the trust with the state, there won't be an additional annual charge, whereas in most states there is an annual charge of from $100 to $500 for each LLC. So this should actually save you money in the long run.