At 22,494 gold, this is way more than I was hoping to pay, but there aren't really many spaces we could trim out to save much.
Right now, I would say we could do without the Smithy (250 gold), the indoor training area (1000 gold), the Common Area (500 gold), and one set of bedrooms (700 gold). If I remove those from the plan, it would reduce the cost by 2,450 gold, or 2,817.5 after modifiers.
[X] Wayfarer's Respite Building Plan
-[X] Wooden Walls & Moat: Cost: 1,920 gold (20 SS x 160 gold x 0.6; ratio of outer vs inner walls of a 20 space stronghold)
-[X] Outbuildings/Open Space:
--[X] Alchemist's Lab (x1 space): 350 gold
--[X] Courtyard: x3 (x3 spaces, upgraded to be suitable for training): 750 gold
--[X] Dock (x1 space; doesn't count against 20 space limit?): 500 gold
--[X] Guard Posts: x2 (x1 space): 600 gold
--[X] Smithy (x1 space): 250 gold
--[X] Stable (x4 spaces; room for 24 horses): 4,000 gold
-[X] Main Structure, Ground Floor
--[X] Barracks (x2 spaces; room for 20 men): 800 gold
--[X] Baths: x2 (x1 space): 640 gold
--[X] Common Area (x1 space) 500 gold
--[X] Dining Hall (x2 spaces): 2,000 gold
--[X] Kitchen (x1 space): 2,000 gold
--[X] Storage: x1 (x1 space): 250 gold
--[X] Training Area (x1 space): 1,000 gold
-[X] Main Structure, 2nd Floor
--[X] Armory/Strongroom (x1 space): 500 gold
--[X] Bedrooms: x4 (x4 spaces, x2 separate bedrooms per space): 2,800 gold
--[X] Storage: x2 (x2 spaces): 500 gold
--[X] Study/Office: x2 (x1 space): 200 gold
-[X] Total: 19,560 gold
--[X] Modified Total (+3% due to location, +15% due to tech limit, +3% due to Winter, -6% discount due to using Fellowship soldiers for some labor): 22,494 gold