Local

Hello, I am new to SEO but am very fond of the idea. I have read a few methods, black and white hatted, as well as found many guides on both (Doesn't seem too hard or time consuming).

I'd like to start my own local SEO service to offer local professional practices.

I am confident in my ability to sell my service (searches are high and competition is low) but am not sure on how to rank their page.

BH or WH?

How long should it take to rank up with ____ BH method?

Could I start with a little BH and transition to WH for sustainability?

If you do not know the product you are selling you are a step or two ahead of the game. Learn the product so that you can offer it in a way that is first hand and know what to offer your prospects.

Figure out how to rank your own sites before you start messing with other people's livelihoods.

Local SEO Ranking is from white up to light grey. Besides the situations, when you need to improve already bad reviews in bulk quickly (God please, not Yelp....) and show some over WOW miracles overnight to impress a new client Actually, I was never sitting thinking should I go white or black. There is always the specific problem you need to solve ASAP with min risk for the client and your reputation.
I would recommend paying attention to the maintaining decent local directories profiles (GMB, Bing Places, Yelp, and about 50+ others) geotagging, local citations quality and quantity, keywords in reviews (real aged accounts, location of the service area of your business, different IPs) and some "near me" keywords SEO ranking work.
And find the right analytics platform for local SEO. You cannot go blind and provide decent trackable results for clients. I would recommend MOZ Local or as the basic option Agency Analytics (the have local SEO keywords ranking).