After doing some more research I came across this in the archives,
What we can now say is as well as working as a labourer he was also doing evangelical work and preaching during his time in Scotland.
This article also suggests he could have been a slave or his parents maybe were.
It is also worth noting that I was told that there were land records where Edward Haig (caroline his mother was listed) had some land in South Carolina.
I can't seem to find anything about his mother or trace any records of her in South Carolina around the time he was born