I prefer to work from the apartment I live in but that only works if you have no-one you need to have live with you, and realistically if you prefer small numbers of longer bookings, because you wouldn't want multitudes of customers in and out of your home and you have to be super fussy about who you see to minimize the risks of doing this. But I do it because the stress of paying for two places would be too much for me, I just don't work hard enough and I'm not consistent enough with my hours.
If I had to I would keep the costs on both my places low as possible, for a work flat you only need a studio, if you are only working from it, no more than a hotel room size place in a big apartment complex, say. As long as its clean and reasonably modern. Though I can see the benefits of a one or two bed work flat I would personally see it as surplus to requirements. And I get about the renting it on the days you are not there thing can be dodgy because extra foot fall and the discretion standards of the other person, maybe consider looking for just one other person who seems discreet and just rent it during work hours (like 9-5) so if its in a building with professionals and no front desk/concierge there will be no-one around to notice?
On smaller things, see if you have a clinic near you who give out free condoms to escorts, I use fishnets instead of stockings for the most part as they are more resilient and though some fishnets can be a bit tacky (although who cares? I'm a hooker not a champagne waitress or news reader) you can get some fancier ones. I only buy a new outfit when I have had a particularly good week and Anne Summers have major discounts at the turn of each season so I hedge my bets for around then. I got a corset for £20 that was £80 for example, recently. I keep a change jar and make cut bucks on wasted things I don't need like take out coffees and magazines I barely read and that extra glass of wine in the evening, and fill the jar and wait till its got a good amount in it and then use it towards a tour or an expensive item. Its surprising how quickly it mounts. But these sorts of things are more savings here and there.