I started up a few months ago but bought a round so can't help you with building the round. I would start trad if money is an issue you can always go wfp later. I also think being able to trad makes you a more rounded window cleaner.
As far as equipment goes:
Ladders: go to ladders online
http://www.ladders-online.com/ cheaper than the rest, good ladders next day delivery.
I have 3m double extension trade ladders. I got this size purely because i know it covers everything i do. You may want longer such as 3.5m to cover more jobs cost around $90 Excuse the dolar signs its means pound but my laptop is from Australia

BOAB: Bucket on a belt, essential piece of kit to hold your TBar applicator and squeegee cost bout a tenner
Squeegee: i use 12 inch fairly cheap.
T BAR: Same as squeegee doesn't cost much.
A few scrims. I use one or 2 per day you will use a lot more when your first starting up so say 6 or 8.
Glass Scraper: only a few quid.
Sill Cloths: Make from old towels.
Soap: Fairy liquid
Bucket: Square one for window cleaners, cheap.
Pouches for belts. I use 2 one for scrim one for sill cloth.
Roof Rack, Mine cost about $100
Ladder rack: $20
Can't think of anything else off hand your start up should cost around $300.
You can get all this online.
Best thing i did was spend a few hours with my local window cleaner. He increased my speed no end by teaching me the correct technique, i can't reccommend this enough.
Good luck
