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A home equity loan is usually a mortgage that is in 2nd position on title, behind a 1st mortgage. They can also be 1st position on title, without any other mortgages against the home. Due to them more commonly being in 2nd position, the qualifying requirements for them are a little tougher than 1st mortgage programs, and they almost always require a credit score.
If she still wants to obtain a mortgage without a credit score, she'd need to look into a 1st mortgage program, most likely an FHA mortgage. FHA mortgages do not require credit scores if someone has sufficient non-traditional credit. Sufficient meaning 3 current forms with the last 12 months being paid on time. Examples of non-traditional credit would be rent, utilities, cable, internet, non-payroll deducted insurance, and even putting a steady amount of money away in savings.
Home equity loans have very little closing costs, whereas FHA's closing costs are fairly significant. She'd be able to save herself a lot of money if she was able to get a credit score (and ideally she'd want it to be 680+) and go for the home equity loan route. What is the reason she wants to obtain a home equity loan?
If your sister doesn't need to move into this home soon, then I'd recommend your mom wait the 6 or so months it'll take for a credit score to generate and look into obtaining a home equity loan at that time. If this is the only way your sister can obtain shelter and she'll be homeless, then the FHA cash out route would be the way to pursue.