If working on Mustangs is a hobby, don't make it a business. Keep it enjoyable for you. Also, keep in mind that Mustangs (and performance cars in general) are a hobby for many, so when the economy takes a hit, spending on hobbies tends to go down.
Depending on the field of construction, work may or may not dry out depending on if you are building new houses, or in an in-demand trade like plumbing. I was an electrician for 10 years and through 2008. We slowed down but still had enough work to stay busy and well-paid.
I worked commercial construction from 1977 until 1997 when i just couldnt take it any more ,destroyed both shoulders and elbows ,made very good money but wore me down .
I restored mustangs from 1976 until now . It was a lot of fun at first ,everyone was nice but somthing changed around 2005 and people became ,whats the word i am looking for ...obnoxious ! It is not like it used to be so i would recamend working on your own cars because the new people attempting to want these cars built will suck the life right out of you ,sorry for the rant and when you do find someone that is a pleasure to build a car for it is a great experiance
Working on other people's cars doing things they want them done is far less enjoyable than you might think....especially when it comes to vintage mustangs where everyone thinks they are made of gold.