Lock slot on side of doors

[Possom]

Would it be a relatively simple (and inexpensive?) job for a joiner to place a section of timber into the lock slot on the side of a couple of old doors so that a rim lock could instead be placed on the doors?

 

[Tigercubrider]

Not a pro but relatively simple to do in most cases. However it will take time, and time is money.
You need to realise that you will need to pay for at least half a day's labour. Two doors is probably more attractive than a single?

Possibly cheaper if you can get someone to collect the doors and take away to work on with a reasonable lead time (or deliver to him and collect later?)

A mate is a mobile chippy and I imagine that it's the kind of thing he could do in his garage in the evenings rather than waste daytime hours