Best buy would be a used 80s road bike with quality butted Cr-Mo tubings like Bridgestone 600/700 or Centurion Ironman (23-25 lbs). The Bridgestone has a more relaxed touring geometry (less twitchy). I've seen good specimens @ CL for $350-$450.

You can upgrade the rear wheel to 8-speed cassette for about $180 (DP18 rim $25, DT 2.0 mm spokes/nipples $32, Shimano 105 hub $55, cassette $18, labor $50). Add an $18 8-speed Alivio trigger shifter if you want index shifting.

A strong rear wheel with the proper cassette with allow you climb hills and fly on flats. Once you have the bike, you can post here for tips on how to re-lube the hubs, bottom bracket, brakes, and headset.

Take close-up pictures of the front chain wheels, rear sprockets, bottom bracket, and headset of the bike that you want to buy. Post them here and others will provide you constructive input about the condition of the bike.

If you want a super heavy duty bike with dirt road capability, then check out the steel MTBs. Keep in mind that an upright riding position is not ideal for long distance commuting.

I'd offer $200 max for the Raleigh. Not much tire and and freewheel selection available. Components are just OK.