Do both, obviously if u got the money buy a wfp , but first u need to get the basics right, learn ho to do trad window cleaning, there are lots of tips to learn that will make you faster whilst still giving a good service.
use youtube for some tips , thousands on there.
when your cash flow is there and only if u need it get a wfp system.
i was trad for years b4 i started back and made a proper good go out of it and went out and got a wfp system, and thats as i had to as i won some council contracts and needed it.
i stiil clean at least 100 houses a month just on trad method
hope that helps