You can probably build one cheaper. The nice thing about the premade ones though is that they tend to be airtight and you can get away with murder with wind direction. They also tend to come with window systems that are nearly silent, which is handy when things don’t go as planned.
Hard to build one as nice for much cheaper than this guy sells them. He mills his own lumber and buys in quantity to keep price down. My brother bought 2. They are nice. https://blackdogfarmllc.org/index.php?page=blind
That will probably be the best hunting you have ever done. Nothing like watching kids get excited over the wildlife.
And those memories will be his best memories! Just like all of the boating and fishing he gets to do with you.