But let's separate the issues.
In owner financing, the owner serves as the bank. You put down as little or as much as the two of you agree on. Then there's a mortgage for the remainder. It might look something like a conventional mortgage--say 15 years at a fixed rate. Or it might be for a shorter term with a balloon note at the end. Example: You'd make payments as if it were a 30 year mortgage, but you'd have to come up with the balance--typically by refinancing--in 5 years.
With owner financing, you buy the house. The deed is in your name. Then you make payments to the owner.
With so-called "rent to own" (which is really a lease-option or lease-purchase--"rent to own" is a meaningless term), you do not get the deed to the property. The owner holds on to that. You rent the property for a period of time, usually with a portion of what you pay in rent being credited to your purchase price. Something in the range of 10%-25% is often the norm. Then you have the option (that's the option part of a lease-option) to purchase the property. Example: You might have 3 years in which to buy the property at a set price. At that point, you'd go out and get a conventional mortgage and buy the property from the seller.
Tip: Never, ever pay 20% for a lease-option. That's WAY too much. It's all negotiable, but something in the range of 1%-4% is pretty much the norm. Remember: That option fee is NOT a down payment. It's a payment to the seller for an option to purchase. Often, that amount is credited to the purchase price IF you buy. If you don't buy, you don't get it back.
If you can afford to buy today, then buy. If you'll be in a position to buy within 12 months, then wait and then buy. If you feel compelled to buy but know that you won't qualify for 2-5 years, then you might consider a lease-option.
Hope that helps.