@Joshuam R.
The transfer to a single member limited liability company will by default be treated as a disregarded entity for US income tax purposes. This means that the rental income and expenses is reported on your Form 1040, Schedule E, rather then an partnership return (form 1065), C-corporation return (Form 1120), S-corporation return (Form 1120-S), fiduciary return (Form 1041).
You can elect to be treated as a C-corporation or an S-corporation, however, you are then subject to different income tax consequences, and an additional tax filing for the rental income and expenses stated above. C-corporations have double taxation (tax on income at the corporate level, and tax on dividends when earnings and profits are distributed to the shareholder/member), while S-corporations are flow-through (so no double tax). S-corporations are still subject to some corporate tax provisions, which generally make owning real estate not as attractive for long-term ownership.
In the simplest form, a single member LLC offers the best of both - strong legal protections if the LLC formalities are maintained (separate bank accounts, annual member meetings, etc) and easier income tax compliance on your Form 1040 (no double tax, no extra return, no corporate income tax rules).
If you add a partner to a single member LLC (aside from another disregarded entity you own), you then have to file a partnership return (Form 1065).
