For the one you are semi-interested in, if she sells it to you without a realtor and thus discounts it by whatever % she would pay in realtor fees, does that make it worthwhile? It's worth considering. Also, in some states (CA, at least), if you by a house from direct family, your property taxes remain at their old value/basis, which can be a huge savings. DH and I bought my grandmas house (technically from my dad who inherited it) and he tax basis was something like $79k. We paid $330k, but our property taxes continued to be based on $79k. Large savings for us. Worth looking in to.
I agree that you should really try to talk your husband out of this, but if he's dead set, then I'd go with a small discount. If 10% is the local going rate, charge 8% or 7.5%, plus $30/hr for labor. (That wouldn't include standard walk throughs, contacting repair people, and things like that, which a PM would typically do as part of their basic fee.)