This painting of a seascape done in warm tones of yellow and brown
with a driftwood style frame was painted in the 1970's by
an unlisted artist named Gustav. The style is that of
the paintings sold in the sidewalk sales in the US
during the 70's by art importers that had studio artists working
for them in Mexico and South America. This painting would
have a current value of $80 to $100 retail.
Some sites that I recommend for selling are Varagesale.com, Ioffer.com, OfferUp.com, Ebay and letgo.com.
You can also go to invaluable.com or liveauctioneers.com and search their directory for an auction house near you and consign to them.
To finish, I will need you to click the five stars at the top right of your screen and hit the green submit button, thanks!