HELOC and rates/suntrust

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hi everyone i am a newbie and i have a question about a line of credit i want to take on my personal residence. 

i have around 650k equity on a million dollar home with 350k (mortgage + old line of credit combined). i wanted to take a new line of credit of about 500k to pay off the old mortgage and line of credit to be left with around 150k cash for some home improvements. i have been seeing rates around 5% but suntrust (link below) has an offer for 3.75% plus -.25% discount if paying from a suntrust account making the rate 3.5%.  want to know if this is too good to be true or if this 3.5% is on top of some other rate. i really don't know much about this. 

and also i only make 70k a year with no debt is it possible to qualify for 500k with such little income? i originally just wanted 150k loan cash but they told me i should apply for 500k and pay off the other two loans for a better rate with them

https://www.suntrust.com/loans/equity-line-of-credit