To get case 1 you need to effectively be working full time overseas until the end of this tax and then to the end of the next. If you can't satisfy this then you will be unlikely to pass case 1.

Otherwise you're stuck relying on case 3 or the double tax treaty

The last one comes with a caveat that tax may be due in the host country, so would need separate advice

That being said, if it is reasonable and justified in that the amount of hours she is actually working and the work done does justify the wage then box 28 'cost of services, including wages'.

Just make you have records of hours worked and duties in case of HMRC review.

It was already pointed out in another post that this was likely a sham arrangement and not deductable. What has changed?

Can get the link, but if you Google RDR3 pdf there you can find the old pdf version of RDR3. If you go to 3.10 it has some guidance on what constitutes work. Maybe it's just me but I can't find this in the new HTML version of the guidance

Think the RDR3 appendices has some guidance on it.

It specifically mentions that voluntary work is not work (devil in the detail obviously)

Guess the longer term aim is the view that real estate will grow in value faster than stocks and bonds, the rent received may give a small profit after expenses.

I'm not a financial advisor so this may or may not be true. Most I know caution against it due to liquidity.

Any specific reason why you rented out then moved back in, potential for some periods of deemed occupation.

Would either need to break UK tax residence which will only realistically happen if they are working full-time in Turkey for at least until the end of the current tax year and then to the end of the next tax year, or they give up their UK and relocate. Beyond that non residence under the UK Turkey t...

Depends on the tax treaty, without treaty protection however it's deemed UK sourced and taxed here (and potentially where you are resident as well, but there should be some form of mitigation, usually by allowing the UK tax as a foreign tax credit).

Where are you resident?