So I'm looking to start making and selling cakes at home. What steps do I need to take to do this and what do I have to do/say to ask permission to do so in my council rented property? How did everyone else start doing this for themselves at home? Thanks in advance x

I presume you are in the UK?  You need to register and be inspected by your local environmental health department.  They will expect you (probably) to have done a Level 2 food hygiene certificate (you can do them online).  You will need to inform HMRC that you are self employed and therefore will need to complete an annual self assessment form.  You should probably take out public liability insurance.  As you are in rented you should check the terms of your lease.  If you have home insurance you should probably also let your insurers know.  

Sketch out a business plan...doesn't have to be an elaborate formal one; but a framework for your goals; what you intend to produce; identify your target and marketing plan; sources for ingredients and supplies both locally and mail order.  

You need to research and be in full compliance of any and all cottage food industry laws for your state and county.  Not all states have cottage food laws; if your state does, then the state's public health department will most likely be the state department charged with implementing the law.  Your county health department should also have the information.  If permits and licenses are required, you'll most likely go through your county health department to obtain them.  

most states have a list of allowable foods that you can produce in a home kitchen.  some, states, like my state, requires purchase of ingredients only through approved sources--which isn't well defined, but you will need to know where or not you can pick berries from your neighbors garden to make a cake filling.  Then there's compliance with labeling laws (that's federal).  Most states just say you have to be in compliance with federal labeling laws.

setting up a system for record keeping before you star is important.  Most states have a maximum income allowed in a home based bakery business.  The thinking is if you earn beyond the allowable income, your business should be subject to the same regulations as commercial producers.