Newbie: Have idea of using HELOC to supercharge my REI start

[Antonio Martinez]

Hello Everyone.....i just joined this forum bc as i was scouring the internet over the last couple of day this forum kept popping up as full of information. so thank you all for letting us newbies access all this wealth of info. my situation is as follows. 

current mortgage balance on 2 family home: 360k @ 3.75% for 30 years ($2300 montly PITI)

current market value by a local Credit Union: 553k

joint Debt between me and wife: 77k (majority is student debt)

Montly Debt payments: $1265.00

Rental Income from Duplex Apt upstairs: $1700.00

my idea is to get a 10/20yr HELOC for 80k to consolidate our Debt obligations and then paying only the interest on the HELOC (5%) is a 333/month payment.

basically converting our 1265.00 montly debt obligation burden into a 333.00 burden. we would be responsible for the mortgage (2300.00) and the HELOC interest payment (333.00) which is 2633.00
this minus the 1700 rental incomes makes our montly home burden 933$ dollars.

our monthly income combined is approx 6k after taxes but we also have daycare and food and car insurance and the like. 

my idea was to basically transfer and extend our current debt to a lower montly payment as we plan on moving in 1.5-2yrs and then fully renting our 2 family home which should bring in about $3500 a month conservatively (city property with 2 parking spaces). the rent of the home would cover both the mortgage and HELOC interest payment and STILL be positive cash flow

am I wrong to think that then the HELOC would basically be paid by the Tenants and not me....in a way i would have transferred our CURRENT debt to another debt vehicle which would then be paid by someone else. 

the plan after paying all of our non HOME related debt would be to save aggressively. i am thinking 2k-2.5k a month should be doable. although i have also thought about aggressively paying down the principal on our primary mortgage instead.

am i missing something. i know people dont like HELOCS bc of the variable rate...but is interest rate important when someone else is making the payments? i also know people dont like them bc you are turning unsecured debt into secured debt....but that rests on the premise that you default...i dont plan on defaulting and given our situation...it would take a series of COMBINED catastrophic events for us to find ourselves in a position where we cant pay 2600/month. 

i do understand that by using the HELOC in this manner...i end up paying a lot more over the long run but again....does it matter how much is paid when it is being paid by someone else? in a sense....instead of using CURRENT real dollars to pay our debt....we would end up paying it with future money that would have been created out of nothing (EQUITY)

what are your thoughts?

thank you all in advance for your time.