An inability to bring on new talent, junior or otherwise, is a symptom of lacking essential documentation. If I can't come into your office and have a copy of your software running or successfully compiling on my machine in less than an hour, something is very wrong with your documentation, tooling, or (lack of) build process.
"Here's Jim. He's our Widgitsoft guy. He's the only one who works on Widgitsoft. The system is entirely undocumented because Jim knows everything. Yeah, development has been slower than expected lately. Yeah, it would be nice if we could bring on a contractor when necessary, but getting to that point would be a lot of work, and we'll always have Jim."
"Here's Jim. He's our Widgitsoft guy. He's the only one who works on Widgitsoft. The system is entirely undocumented because Jim knows everything. Yeah, development has been slower than expected lately. Yeah, it would be nice if we could bring on a contractor when necessary, but getting to that point would be a lot of work, and we'll always have Jim."