I understand you want to keep costs low, however hosting Mautic on your own computer is a no go, a cloud VPS will cost you as low as $10/month or even $5/month.
Another no-go is to use your residential or company email service for sending emails.
You need to use an email marketing service. There are a few mid-quality marketing email providers that offer you lots of free emails per month. If you are not sending that many emails, Sendgrid is top quality provider and will give you 2K emails for free each month.
Amazon SES offers you 65K emails for free each month, coupled with the free tier, you can get Mautic running for no cost at all for an entire year.
I’m already working on a guide about how to run Mautic for zero $, in the meantime, here are 2 other posts you might find useful: