Got a wee rental that’s empty so we’re giving it a spruce up. Woodwork is all white gloss that has yellowed in places as it does.

Is it worth keying in the wood then using a water based gloss or eggshell to avoid the yellowing? Or just stick more gloss on knowing that we’ll need to do it again anyway when the next tenants move out?

Definitely stay oil based. Granted water based doesn’t yellow but it’s not as tough, will have more brush marks and it gets grimey,especially around door handles and on banister rails.

Crown Solo gloss is a wonder product. It is really good. I’ve been using it professionally for over 10 years and have used gallons of the stuff. £20 for 2.5 litres in Wilko. Don’t get it confused with Dulux Once which is an awful cottage cheese like paint.

We had ours painted properly when we got it four years ago so it all still looks ok, probably better than our home!, so depends how you prioritise your cash flow. We are happy to provide a very nice place rather than OK as we want the place to stay in good knick in case we ever downsize into it and tbh I’d rather be a nice landlord than not ( that’s not a dig at you )

Unfortunately cash flow won’t allow getting someone in to do it, but the wife and I are pretty handy and confident we can do a good job. We’ve always done our own decorating. We decorated it about 3 years ago, and apart from yellowing it still looks quite good, but we’re having new heating, kitchen and flooring put in so would be silly not to to paint it again.

Hope you’re taking the opportunity to paint the skirting before the new flooring goes in. Dead easy when you don’t need to worry about spills. Will require only minor touch ups to fix damage during reflooring.

When you say it has yellowed in places what do you mean?
If knotting was not used on any knots present in the timber then the resin will come through as yellow marks
As in picture below
http://www.ronseal.co.uk/home/interior-wood-and-furniture/knot-block-wood-primer-and-undercoat/

Oil based paints yellow more with lack of sunlight i.e behind furniture etc. Knot bleed happens when no knotting solution was used at the priming stage. However Zinnser make a shellac based primer called B.I.N. if you paint that over knot bleeds before further coats of paint it will seal the knot.