Looking to buy a Piano.. Piano players help??

[poopie boy]

Okay so I am looking to buy an acoustic piano, but I don't know anything about them. I love to play my guitar and I want to get into piano now.

I am looking to spend no more than $300.. I just want something to start off with. I am looking to get the best possible sounding piano I can get for this amount of money. My friend has a Baldwin upright that I think sounds just fine.. His cost him $150 on ebay.

What are things I should be looking for when buying one? I only have room for an upright but a baby grand is not completely out of the picture if it will sound better than an upright for the money. I have seen the prices of babygrands in the thousands, but here and there I come across a craigslist or ebay listing that is in the price range im looking for.. should I stay away and just go for the upright?

What are brands to look for? What age is usually good for a piano? Any insight from experienced players?