Can I buy a flat for a friend to live in?

While your are very kind and your intention is noble, this would be a poor business decision (if by saying " not interested in making money", you intend to run this as a charity then do what you wish).

I am afraid a trouble free tenant wouldn't have left the mortgage not paid off into her 60s and made little provision for retirement (hint:pension credits). She could also have taken out a lifetime/reversion mortgage and kept her home.

But your money, your choice.

Renting to someone you know can work well or it can be a disaster.
Saying you don't want to be a landlord isn't a very encouraging statement. If you are a landlord it is a serious undertaking with numerous legal responsibilities.
Whatever rent you charge needs to be sufficient to cover unexpected repairs bills and unforeseen charges the government suddenly invent for landlords.

At 73 years old your friend is old enough to apply for Council retirement housing or most almshouses. It may take a while to be successful but either of these options would be more flexible should physical or mental health deteriorate for either of you.

I'm afraid that your idea is fraught with problems.

If you do decide to proceed you will need a good legal agreement.

Who will own the property?
Who pays for repairs?
If you own it you will be the landlord - that's a fact.
If you own it you will have liabilities for safety that cannot be readily transferred.
If you own it and require funds at some point, will you be able to sell? Can you make your friend leave? What if either of you become ill or die - how will matters be dealt with?

I'm sure a solicitor would have many more points to raise.

You can help, of course.

However, if you take a penny in payment, you will be the landlord, with all that entails. Mortgage interest isn’t an allowable expense.

You would also be liable for higher rate Stamp Duty Land Tax.

Could she move in with you or could you buy a home that is suitable for both of you?

help her to find or source council accommodation that better suits here needs now AND the future.

A flat is no good long term if her health deteriorates etc if it has access issues etc. It also means she will become isolated and more dependent on help coming in. If a more social type of accommodation can be sourced now then this mitigates this in the future.

Voice of experience here - NEVER go into business with a friend and NEVER loan a friend or family money. If you wish to do so GIVE them the money with no strings attached.

You will always be responsible, they cannot even get building insurance themselves . Even worse you will be a landlord if you take any money and even if they don't complain another relative might of they could approach an official looking for help with something - they will quite happily throw the book at you regardless of your generosity and kindness. A small farmer has recently been fined under similar circumstances.

I bought a 2 bed house for a friend/chap that worked for me to live in with his girlfriend in 2006 as the rent on their studio flat had just been massively increased. The house was ok, but not fantastic. However, the rent I charged was below that of a studio flat, and initially he was going to do some diy and improve the house in return for the really low rent and security.
In 7 years he and his girlfriend did NOTHING to the house except let it get dirty and overgrown outside and by the end she was becoming like any other tenant and quite demanding and moany about any issues the house had. Luckily they decided to move on.
I spent 2 months doing the painting, gardening etc that they were going to do and let the house for 3 times the rent they were paying.
They are no longer my friends. So weird. In 7 years I must have subsidised their rent to the tune of at least £70k. Never again.
My advice now to anybody in a similar situation is to do everything at market rates and then if you feel like giving the person a massive lump sum (like £70k) later do that and they will actually appreciate it!

I think you're very noble, but unfortunately, there is going to be more and more of this... people are going to be in their 50s, 60s, 70s, 80s, 90s... and STILL RENTING / sofa surfing.

I had a client whose partner of 30 years died (they were never married), so in her will she made a provision for him to be able to borrow money from her estate to buy somewhere, until he passed on... He couldn't find anywhere within budget (he's in London).

BUT, having a few friends in their 50s, I started to look into it for them because I know more and more older people in the rental trap. They don't particularly want to share a house like they did in their 20s... but thats what their budgets are dictating...

There are places to rent, for way below the usual market rent, and it's only for people who are 50+ or over 55, or over 60s, so I'd look into some sort of specialist type housing like that for her. It's going to be an increasing problem as we're in an aging population, there's a lot of 'gray divorce' (thats retired people getting divorced), and so people need to live separately...

I'm convinced, half the housing crisis is because people cannot live together like they could a generation ago. People want their space. They don't want to put up with nonsense. It does effcet your mental health, so I don't blame them.

You would be subject to a massive amount of regulation that you dont even know about and sadly you can rely on many letting agents to have your back. In future a simple mistake that does no harm to anyone will cost you a £7000 penalty in the first instance and £40000 in the second instance and some will also require up to 2 years rent to be repaid. Id suggest you either gift her the property or find another solution, such as standing as guarantor for a tenancy with a more experienced landlord.