Sharp collected and arranged folk songs for piano and sold what he collected that means he did not have independent means like BaringGould
he relied upon sales of his books to finance his collecting that means he was a professional collector
defintion of amateur engaging or engaged in without payment; non-professional.
the whole point is that Sharp, not having independent means. was restricted financially as to where he could travel, because he had to live on the sales of his books, therfore being professional restricted his ability financially to travel too far afield
this was how he financed his travel to appalachia..... a philanthropist helped [ In the final weeks of 1915 Mrs Storrow wrote to Sharp offering him the sum of $1000 to use as he saw fit in the mountains. Sharp accepted at once and began preparation for his first collecting trip into the Appalachian Mountains.]
the above was a quote from an article by Mike YATES in musical traditions