So essentially, the answer is skyscrapers, scrapping second homes, and legalising and thus ensuring tax is paid, on the sex industry.
High rise buildings frequently bring social issues with them: they aren't really suitable for families and for elderly people.
Empty homes aren't generally kept for tax reasons but as letting properties, and preventing people from owning them is not going to solve the housing crisis but add to it. People will always need to rent.
The sex industry can be characterised by the few who earn a lot from it - escorts - and to consider them first, if sex can be seen as a transaction, how could one tax it? It's unlikely the 'service users' would be willing to pay by debit card or cheque even if the woman insisted on this. Escort agencies pay tax: individual workers generally do not. This would not change.
Those who are more vulnerable would not stop being vulnerable because of tax. A red light district with a heroin addict charging £20 for sex (I worked with these women; I know that's the going rate or was in 2008 anyway) is not going to hand some of it over to HM tax revenue.
At any rate, we are hugely digressing! We cannot keep adding to our population without this having an impact and in some of those instances that impact will be negative. If you are affected by it, it is not racist to point this out.