Straight ownership or LLC

Go with an LLC, if only to protect your other assets if, say, a tenant's guest falls down the stairs and is awarded more than your building's liability insurance will cover.

At five or six hundred bucks, plus the cost of advertising, to form an LLC, there's no reason not to do it.

No ownership structure is perfect, though. A Business Law book would help, or something more specific, like http://search.barnesandnoble.com/Real-Estate-Finance-Investments/William-Brueggeman/e/9780073377339?itm=1&usri=0073377333

I'm with NWT. LLC.

It's a no-brainer that you should incorporate.

However I'd discuss with an attorney whether it makes more sense to do an "Inc." or an "LLC". There are still advantages to an "Inc." over an "LLC" -- although at the moment I'm not sure what they are. Trust me, it'll be $500 well spent.

LLCs, so each building is a separate entity.

When you say you are thinking of entering into the LL biz, what is your plan? Are you looking to purchase full ownership of buildings? Are you thinking of managing them yourself?

If you are coming to SE for advise like "LLC or not", I would recommend investing in a couple of other people's properties first and getting a good feel for how things work from that perspective before taking it further...

does it matter whether we are talking about a 1 family or 4 family or 29 family or condo or coop

OK, now your ignorance is showing.

Co-ops are generally not available as investments.

I think you'd better start doing your homework before laying out any cash.