Started a general contracting business:

Looking for the best, affordable application to use for a start up business. 
Not a lot of steady income at the moment, but I'd like something that won't turn my clients away from paying online and using their credit cards.

I've noticed many programs charge interchange fee + % + additional $0.30+ per transaction.
Ive noticed a few programs charge 2.9%+ of the overall cost.

Many clients will be spending a decent amount on the construction projects and these additional fees may price me out the door.

Trying to stream line the process by emailing a proposal, client electronically sign it and insert their deposit in order for me to schedule the job. Then I invoice payments in phases like the middle of the project or upon completion, depending how large of a job it is.

Currently, I'm using Wave Accounting, but they just increased their payment processing option at 2.9% + $0.60 per transaction.

I'm looking for a way to limit costly monthly subscriptions with multiple service providers:

-to email pdf proposals, & invoices, with electronic signature & an all in one feature for the client to pay the initial deposit in order to schedule the job.

I have no explored much of Wave Accounting ability yet, still fairly new.

Any advice to build this model up for success?

Thanks in advance!