Why can’t I open the console in Oblivion

One of the most quirksome features of Oblivion is that everything scales. It doesn't matter where you are -- whether invading old undead-infested forts, or clearing oblivion gate after oblivion gate; the champion arena matches, or facing off against Manimarco the King of Worms -- all creatures are scaled to give you approximatley the same level of difficulty throughout.

So to answer your question, there is no proper level. However, the game can be a bit brutal at the early levels before you can build up enough of a health buffer to make fights more drawn out affairs. How are you building your character? (Stackexchange has some good questions re: oblivion for these very things!).

You should find these links useful:

Playing a sneaky character in Oblivion

Character Building tips for Elder Scrolls IV: Oblivion?

The unofficial Elder Scrolls wiki has a good database of the traditional houses (like those that can be purchased in each of the major cities) as well as a list of the houses that don't count for your "houses owned" statistic. The wiki also has a complete list of non-respawning containers; normally, the contents of each crate, chest, and container gets reset and randomized every 3 in-game days.

Here is the page for houses;

Here is the page for non-respawning containers

If you can't find your stuff stored in either the "free" houses, or the safe containers, you may simply be out of luck, pending a burst of sudden remembrance.