Can someone tell me if im doing this business right or any advice

[Joshua D.]

So when i first started i bought a duplex for $16,000 put $5,000 into repairs and went to a local bank that lent me a line of credit for 80% of the appraised value which was like $45,000 so i rolled that into my next property. Which i bought for $27,500 put another $3,000 into repairs and got a line of credit for $75,000 and have been keeping this ball rolling for 3 years now. The question i have is with the lines of credit im using the interest rate is variable and is 5%. Would i be better off getting a loan with a fixed term which i have the option at the bank to do. Should i do that? Makes it a little scary thinking the interest rate can shoot up to a crazy number and be sky high. Any Advice would be great.