HGTV does pay for renovations on their shows depending on the particular show. In some shows, they come in and pay for everything. In some cases, they share costs with the homeowner. In others, they are following along on a regularly scheduled renovation. There are still requirements for the free renovations. HGTV may require that you have a certain square footage and a certain amount of space when doing a kitchen renovation, even when they're paying for it.
Let's not forget the taxes that come with this type of money being given. On shows like 'Color Splash,' and 'I H@te My Yard' you are required to pay some of the costs for the renovation. For example, on 'I H@te My Yard' the homeowner will be given a yard makeover for $15,000 to $20,000, but the homeowner has to contribute $5,000 to $8,000 depending on the work that's being done.
Of course there are those shows on HGTV where it's obvious that the homeowner is fronting the bill, such as on Property Brothers.
A video tour HGTV conducted last year of Big Willie's $2.5 million trailer has resurfaced online, and gives Will Smith fans a look at the luxurious lifestyle the actor leads when he's on set shooting films. See more at E! Online.