Free. Answer guided questions in your own words, and get them organized under clear headings for a personal or buddy statement. Nothing you type is saved or sent anywhere.
VA's form for a written statement supporting a claim, your own or someone else's, is VA Form 21-10210 (Lay/Witness Statement), often called a buddy statement. VA lets you submit it online or on paper.
Skip anything that doesn't fit. Empty answers are left out.
Next: read the form's instructions on VA.gov, then copy your text into VA Form 21-10210 online or onto the paper form, review it, and sign. An accredited VSO can review it with you for free.