This is the tool I would start with if I were testing an online idea from scratch.
Systeme.io's free plan does not expire and does not require a credit card. It currently includes up to 2,000 contacts, 3 sales funnels, 1 course, 1 affiliate program, 1 custom domain, and unlimited email sending.
That is enough to build a landing page, collect emails, follow up, and test whether an idea is worth taking further.
Stay on the free plan until you actually hit a limit that gets in your way. If you later choose annual billing, Systeme.io currently advertises two months free.
Referral disclosure: The button above is my referral link. If you later buy a paid plan through it, I may earn a commission. Your price is not increased because of my referral.
Use the free stuff until the free stuff stops doing the job.