Commercial really isn't the holy grail of window cleaning.
Certain sized jobs can earn you very good money indeed, but you also need to be very experienced and understand your market.
It is incredibly easy to get your prices wrong.
I know a man, and he is a regular poster on this forum who earns close to 50k per year doing almost entirely domestic window cleaning.
75 % of my round is scommercial and I don't get close to that income.!!
Learn your trade, build your round and don't be afraid to slap in good prices for domestic work.
It really is a learning curve, and it isn't just about learning how to knock out a standard semi with 10 or 12 windows in 15 minutes (or less) it is also about understanding your market, and that takes time...
Ian