Tax Question for Receiving Money

I'm helping my parents build a new home by funding it out of my own pocket and waiting for them to sell their home to receive funds later.

When my parents sell their home, they plan to transfer these funds to me. Are there any tax implications with this transaction? Any steps to take with IRS?

 

So far, I've paid around 125K for the house. They sold their house and receiving 300K which they just plan to transfer to me. The new house itself cost 350K to build, so 50K will be coming out of my own pocket.

 

When the home is completely built, I plan to transfer the title to them. Any tax implications here as well?

Thanks for your input.