Dear AZ:

You wrote:
> a. You’ll earn more money in an honest way.
> b. You’ll earn more money honestly.
>
> Could these sentences mean:
> You’ll earn more money IF you are honest.
>
That is what both sentences imply.
>
> c. You’ll earn more money in a haste.
> d. You’ll earn more money hastily.
>
> Could c and d mean:
> You’ll earn more money IF you are in a haste/if you act hastily.
>
Neither really make much sense here. “Haste” normally has a negative connotation; it suggests not only speed but carelessness. A common proverb is “Haste makes waste.” Perhaps you could say, “You’ll earn more money quickly”; but because you are already using the comparative for with “money,” it might be clearer to say, “You’ll earn more money more quickly” or “You’ll earn more money quicker.”