In some future, I would like to have some local music played as house concerts at my place. Think small coffee-house type of affair, mostly acoustic or light electric, two voices. Indoors, with 50 people, or outdoors, on the lawn (OK, moss) with maybe 100 (yeah!)

I suspect some bands will have sufficient PA of their own (?), but I would like to plan on having something on hand.

What would be good choices for basic PA system components, given that I start fresh, no legacy equipment.
Pick some up used on CL or such?
In a pinch, could I put a Blues Jr and a newer Bassman 100W bass amp to work in the chain?