Firstly, you need to see a good mortgage broker, as there are hundreds of mortgage products on the market.
I have purchased Buy to Let properties off my own back and through one of these investment clubs. The one I found myself, I had to put down 15% deposit and the ones through the investment club, 5% deposit, but also had to pay them finders fees.
You can buy a property under the guise of purchasing it for yourself, but if you want to rent it out, you still need to inform your mortgage provider, they will usually charge you and administration fee of a few hundred pounds. You should also inform your insurers.
If a property is your main residence, then you do not have to pay Capital Gains Tax on the profits made from the sale. I imagine this would apply regardless of how long you remained at the property.
Capital gains Tax (CGT) is about 40%. You are allowed to make profits of about �9K tax free and any other fees incurred, through the sale, i.e legal fees, renovations etc are taken into account, but after all that, 40% should be paid on the remainder. Tax is less if you keep the property for 10 years, then the CGT is reduced.
I think, but I'm not sure, if you are buying the property in joint names, the Inland Revenue permit each individual to make �9K profit each, tax free.