It is unusual to be able to make a living working in that field.
People don't usually make enough money to live on working in that field.
“People don't usually make enough money to live on working in that field. So I think you need a lot of resolve. （その分野で普通は食べていくほどのお金になりませんから、相当な覚悟が必要だとお思います。）「並大抵じゃない」は “unusual” と言います。「食べていく」は “make a living” と言います。
Making a living in that field is no small feat.
It is no easy task to make a living in that field.
Succeeding in that field takes extraordinary commitment.
「その分野で食べていく」は英語で make a living in that field（その分野で生計を立てる）や survive in that industry（その業界で生き残る）と表現されます。
アメリカ合衆国 
