I'd have to question a local artist being able to generate 50k on a single piece regardless of size... that is a pretty elite territory in terms of valuation.
A lot of WELL KNOWN artists can't get to that point.
Generally, a local artist is priced in a category known as 'decorative'... and that segment is normally priced very reasonably. If the artist has had any major shows or has a quantifiable auction history, then it is much easier to figure out a range of value.
Depending on medium and size, I can probably guess what a range for a piece might be... but that is still no guarantee you would ever make money or even be able to hold value.
A acrylic 24x32 might be in the 900-2500 range for an unknown and this is being generous.
Does this person have a body of work?
Remember when buying Art... buy what you like and not what you think others might like, because at this level you are not 'investing'.