Reviews notwithstanding I would go elsewhere. The media is rife with people who have paid contractors to do this and that and it was half done, not done, or shoddy, with the consumer having no recourse. A maximum I would ever be comfortable paying up front would be cost of supplies, with 10-25% being no worries in this context.
Which reviews are those? Google? Productreview? The company’s web site?
Windows could be a few hundred to a few tens of thousand of dollars, and all companies won’t do cards, especially if they are sole traders or small. Most trades I deal with are EFT only.
In your situation I would use that info to seek a company with more reasonable terms.
