Art today is a fiercely competition business. A successful artist must subordinate his own interests and values to those which are 'commercial', that is to say those that sell. Many young men and women abandon the field, unwilling to serve the interests of people with means and no taste!
That was Blake's dilemma from ages 23 to 43. For 20 years he struggled to make a living for Catherine and himself while remaining true to his Visions of Life. From that dilemma he was hopefully delivered in 1800.
An affluent man commonly referred to as a poetaster named William Hayley invited William Blake to occupy a cottage on his property at Felpham, a seaside town in Sussex. William and Catherine moved there with much enthusiasm hoping to get away from the 'dog eat dog' commercial milieu of London. But their enthusiasm was short lived.
Hayley proposed to engage Blake in 'profitable' art work such as painting miniatures, and he uniformly discouraged Blake from pursuing his Eternal (non-material!) interests.
Blake endured this travail --an internal one-- for three years; Hayley was kind, trying to be helpful (Blake decided that corporeal friends are spiritual enemies.) (Milton 4.26 Erdman 98).
In 1803 the travail ended; read the letter to Hayley (Erdman 756). It appears that he was miraculously delivered from the stress of 'serving two masters'; he was soon back in London. A truer friend named Thomas Butts bought whatever Blake chose to paint. The Shoreham Ancients (Use the browser to see this article; if you page down instead you may get an ad for wikipedia.) gradually gathered around his house to discuss his work, and to support Blake in other ways.
We are basically indebted to Butts and the Shoreham Ancients for the tremendous inheritance that our poet left for us.