Dose anyone know if you can download hearthfire to a usb memory storage device and use it?

I have formatted it for a xbox storage device and it says it meets the recommended xbox performance requirements. i have been getting conflicted replies from other sources so i would just like a straight answer please help me.

Yes you can. I have all of my DLC on a USB (including Dawnguard, and DLC from other games). You can also put some DLC on your HDD and others on a USB, and the Xbox will find all of them and make them available for use in the game you are currently playing. This is unlike your savegames, where you specify which device your savegames are on, and the game only looks at that particular device. I think this is because it enables the player to have one player character on one device (e.g.) your HDD, and then allow you to have another set of savegames for another character on a separate device (e.g. a USB). This reduces conflicts between savegames that have the same name that appear on multiple devices.

On a side note, you can even put the Skryim 'Title update' (i.e. patch) onto a USB. When any game runs, the Xbox looks at all connected devices and searches them for patches and DLC, and (with reference to patches) will use the latest version it finds. Thus, if you have multiple patches on different devices (e.g. one on your HDD, one on your USB), the game only uses the latest version and ignores all others.
I find putting the title update onto a USB stick marginally reduces loading time. This is tested in the case where no DLC is available, and I compare it to loading times when I have the patch on my HDD along with the game also installed to the HDD. If I put the patch on my HDD, it seems to take marginally longer to load the game. Not sure why this happens. Try it yourself.

My wife told me to ask you all and see if one profile downloads the hearthfire DLC if all profiles on that xbox can use it or dose she have to purchase her own?

That is a good question. Typing "does xbox dlc work on all profiles" into Google provides some interesting information. After reading through some of the results, it looks like that as long as the profiles are all on one particular Xbox, then DLC downloaded onto that Xbox will work across all profiles (so you only need to buy it once). However, as you can see from reading some of the results from google, if you then try and take your Harddrive for use on someone elses Xbox, then the DLC will only work for the profile it was downloaded to. This is just copy protection to prevent someone downloading DLC once and copying it to many other Xbox's. But for your purposes, it looks like that if you download Hearthfire once on your console, then both you and your wife (who I guess have different profiles but use the same console) then Hearthfire will require only one download and you can both use it.

My son has a single profile he uses that is a Live account, and I had him get our DLCs (DG and HF). I use many other profiles on the same box (one per character, none of them Live BTW), and both DLCs load for all my characters as well as my son's. So, enjoy!