@Syed Shah a new appraisal will be issued at the time of applying for a refi or helec.
here is the comparison based on a $200,000 house
Refi: cash out refinance. lets assume you'll get 80% for the sake of this comparison. so you can take that $160,000 and buy another house that would be free and clear lets say for $140,000 plus closing costs and minor repairs lets call it $150,000 with a remaining $10,000 in reserves( lets assume you just pay retail for the house so we don't complicate things)
so your total property values are $340,000 minus your $160,000 loan so your property equity is $180,000 plus a $10,000 cash reserves but in order to access that equity again you either need another cash out refi or to pull a HELOC.
VS
HELOC; revolving credit line lets call this one 80% as well so $160,000 you take $28,000 of this for a 20% down payment on the $140,000 house and put another $10,000 up for minor repairs and closing costs your at $38,000 all in and then have a lender provide the other 80% leaving you with a loan for $112,000
so now you have properties that are valued at $340,000 minus your $38,000 Heloc minus $112,000 loan your left with $190,000 in equity and a remaining HELOC of $122,000 that can be used for acquiring more cash flowing property or flips.
so its a higher amount of leverage but I always recommend focusing on paying back that HELOC when acquiring rentals so you can free up that bit of cash flow from your expenses then go purchase another rental using the same amount until a bank stops you then go after owner financing with 80%LTV+
hope this helps!