After investing 500 gold (SpeechPerk) in his shop, Lucan will have a total sum of 10,000 gold or more. After his funds are depleted, you can either wait for 48 hours to get him restocked, or if you save your game then kill Lucan Valerius and then reload to the save before he was killed all his money and stock will be restored (works with all merchants). This is a much easier way to get rid of huge amounts of items than running around to every Store or Thieves GuildFences. Patch 1.9 “fixed” this exploit; after installing this patch, Lucan will only have 1,250 gold after you invest in his business.
If Lucan is killed, his sister Camilla will take over the store.
If both Lucan and Camilla are killed, no one will run the store.
After completing The Golden Claw you can marry Camilla Valerius. However if you want to marry Lucan you must use console commands (only if you wear the Amulet of Mara).
Upstairs books "Song of the Return Vol 2", "Song of the Return Vol 19", "Song of the Return Vol 7" and "Song of the Return Vol 56" can be found. However, taking them will be considered stealing,unless you marry Camilla.