Go to Merwin Memorial in Allston-Brighton. They only do acute care & triage. No appointments. No frills - and definitely no warmth/patience for humans - but they provide at-cost care.
If you schedule a daytime appointment in advance with their regular vet service (NOT the 24hr emergency center) they already have some of the lowest prices around. To get an actual low income assistance, you'll have to apply for (and be declined for) Care Credit first. Then you'll have to speak with their licensed social worker to work out the details.
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