Owner finance typically means that if you can't qualify or don't want to use normal bank type financing that the current owner will potentially finance the home for you.
You want to be extremely careful in this situations as I often see they are not valid. I've seen cases where they already have an existing lien and want you to pay them and then they pay on that note. This can be trouble if you pay, and they don't Make sure in these cases that you use a realtor and close at a title company. Don't give any money directly to the seller, but make sure any deposits are put through a title or escrow company.
Lease to Own....perhaps possible, but I personally don't like this idea. In my experience few people end up buying. This presents a problem as your contract normally obligates you to buy and puts your down payment at risk if you don't. If you want to rent --then do it, RENT. If you want to buy, then BUY, but don't mix the two. We've recently taken steps in Texas to prohibit these types of transactions. There are still people advertising such schemes and think they have a way around it, but the intent and content of the law is clear-NO RENT TO OWN. There's a reason for the law and that is that there were too many bad guys out there taking people's money in a lot of different ways. As a person wanting to rent you put yourself at some risk agreeing to these transactions.