This is common in Latin, as there are genders for adjectives therefore "stultus pecuniam semper laudat," means "a foolish [man] always praises money." We know that this is a man as the adjective stultus is masculine. Therefore, could we say in French "Un beau veut toujours d'être sur son trente et un" instead of "Un bel homme veut toujours d'être sur son trente et un?"
Yes, many adjectives including beau can be substantivized but the resulting sentence is slightly odd in your example.
Un beau veut... is not really idiomatic although un vieux beau veut... would be.