What @Steve Vaughan said (COOL NAME, dude! Please tell me your middle name is Ray).
If you are looking at financing something else long-term, do a cash-out mortgage. If you need a "cash" fund for opportunities, do a HELOC. Don't do a HELOC for long term just to have the tenant pay it off, that loses the advantages of HELOCs -fast cash, available any time, but floating/higher interest rates- Also, most won't give you a HELOC on a non-owner-occupied home. So if you do want a HELOC get it before you move out.
HELOC - Pros: Fast cash, easy access, flexible; Cons: Floating rates or higher rates, less available equity as cash, short AMMO; use to take advantage of opportunities quickly then find long-term financing later, best to pay of quickly due to increased expense over other financing options
Cash Out Refi Mortgage - Pros: Excellent terms (low INT, long AMMO, higher LTV=more cash), stable/low INT rates; Con: SLOOOWWW to take out compared to HELOC, slower to reorganize/restructure or close out; generally these are good for financing other deals that are longer term and stabilized in nature.