Equilibrium involving both gas phase and aqueous phase
I dare say most equilibrium constant don't cite specific units because the appropriate units are implied implicitly. In the case of the reaction:

$$\ce{R-NH2(g) &lt;=&gt;[aqueous] R-NH3+ + OH-}$$ 

I'd write the mathematical equilibrium equation as:

$$K_{eq} = \dfrac{\ce{[R-NH3+][OH-]}}{p_\ce{R-NH2}}$$

and give the constant the appropriate units: $\pu{mol^2\cdot L^{-2} \cdot kPa^-1}$. (I just picked kPa as one of the zillion units for pressure. Use whatever units you were given the vapor pressure in: atm, torr, mm Hg, lbs/in^2, slugs/furlong^2 ... whatever) 

This is obviously a "overall" equilibrium. According to Henry's law there should be an equilibrium between the vapor pressure of $\ce{R-NH2}$ and the concentration of $\ce{R-NH2}$ in solution. Since you have no way of calculating the concentration of $\ce{R-NH2}$ in solution you can't break the overall reaction into the two different equilibria.