My dad is looking into purchasing a vacation property. I know there's a lot of skeptism about real estate right now but it is a good deal. Although he can afford the monthly payments, most of his cash is tied up in other investments (real estate, toys, etc). This is where I come in. It's a place that I would enjoy as well and I've been considering helping him out on this since I have money for a down payment while he would have no trouble with the montly payments (or paying it off once he sells some of his other assets). We've been discussing a few options:

1) The place costs $100,000. I would loan him $10,000 in cash. He would pay me back as soon as he sold some of his other assets (other real estate, toys, etc). Once he sells these assets, he'll have the money to pay me back and possibly pay off the property, but it will take time (possibly a year or two). I would help him out with his expenses a bit in exchange for being able to stay there.

2) I would put down the $10,000 down payment and automatically become 10% owner. He would be responsible for 100% of the monthly payments on the mortgage. I would pay 10% of all expenses associated with the property (taxes, maintenance, etc)

3) I would give him $1,000 in cash for the down payment. I would then loan him $9,000. I would owe 10% of the mortgage each month. He would owe me for the loan each month, so it would somewhat balance itself out. A bit more complicated but seems to be more fair than #2.

What do you think would work out best? Are there any other options that I am not thinking about?
It's been a place he's been interested for a long time but only recently went on the market.