I just joined the Thieves Guild and I was looking to use the bed I own and a safe storage place. Is the chest next to my bed safe?

It didn't reset on my last thief but I was in the area alot.
I don't know what the reset factors are in Skyrim,if you have to be out of the game cell for 30 days or what.

To test you can put an iron arrow in the chest then leave the area,go to Whiterun and wait 30-40 days.
If the arrow is still there then it should be safe storage.

I've never had a problem using the chest or the drawers next to your bed to store items. Can't say for the rest of the guild chests, but those one have always been safe in my experience.