Eligibility for Medicaid has nothing to do with assets. It’s based on your MAGI (same as AGI for most people.) You can enroll or on and off as your income changes from year to year and the application is basically the same as the marketplace app for regular insurance.
If you buy your insurance through the marketplace, your premiums are determined only by age and whether or not you are a smoker. Your eligibility for tax credits/subsidies is based on your income. I just looked…in our area a Silver plan policy for a 55 year old with 30k income can be had for $0 or $7/month net premium. Since payments are deducted automatically, an insured person is unlikely to let that slide.