As the official word solventa means "pagokapabla", capable of paying, and of course qualifies a natural or legal person, I would propose for the liquid capital solventiga, because according to my (layman) understanding liquid capital is such capital which makes the owner solvent.
Another possibility would be neligita (in the meaning 2 of ligi according to PIV: "limigi ies liberan agadon") or neblokumita.
EDIT: I just looked it up in the huge German/Esperanto dictionaries by Krause. He also has likida, so this is a real word, not a typo, I found it also used a few times on the Internet. But I don't know whether it also has the two meanings of English liquid. As my proposals above rather aim at the first meaning, a clear for the second meaning would be kontant/ig/ebl/a.