Are there and penalties for selling a house BELOW market value?

[Robert Lee]

Hey there,

Say I have a property worth $100k. I want to sell it to a relative/friend/anyone for $50k. Will either I (seller) or the new owner (buyer) incur any taxes/penalties? In an ideal world, I feel like I should be able to sell something I own for whatever I want to but I know Uncle Sam tends to think differently at times.

Any help is appreciated!

Thanks