@Amy Wei Ru Chang, LA investor and Realtor here...I think you should use $300K as a down payment and borrowing the rent of the purchase price.

Joshua,  I understand your point of using the HELOC as 2nd which may be close to accomplishing the lowered total interest payments but in the end, anything you push toward your traditional is locked up and not easily accessible when opportunity knocks.   

I am a first time real estate investor looking the following property : https://www.redfin.com/OR/Forest-Grove/2418-Cedar-Cir-97116/...its a pretty large duplex in Forest Grove OR,  the trick is though, its on a lot zoned for a 4 plex so I am lookinginto house hacking, converting into a triplex, then living in one unit while renting out the remaining two unitsThe left garage has been converted to living space, with a living room, half bath, a laundry room with a sink and some counters/cupboards and a bedroom, it is a part of what was an existing 3bd unitIf I were to acquire the asset, I would first attempt to convert that space into its own unit The line items as I see (be in mind, I am totally new to this) would be to >put up dry wall where the door to the rest of the house is,>add a shower to the half bathroom >install a water heater in the adjacent 3bd unit> install a kitchen in the laundry room, (stove , oven , sink, counter space)>add a shower to the half bath Assuming I can convert it to a 3plex, I could at-least cash flow on my investment after I leave My plan would be to put minimum down payment of 3.5% (FHA loan) that way I can have a decent amount of capital free to do the renovationsThe only concern is when I crunch the numbers to get my ROI, I have no idea how much its going to cost to convert the additional living space to a third unitAny experienced investors here know how I can estimate this before I try to make an offer?

Trust in the expertise of the sponsor or syndicator to handle the operations while you focus on your other commitments.3.

You take the monthly rental income and divide it by the monthly payment (principal + interest + taxes + insurance) and if that number is greater than 1 you have met the basic requirement for DSCR.

This program offers funding up to 400K with a 660 Fico, and at least 27K in yearly W-2 income.No down payment, no Collateral, no proof of funds, no closing costs.

If you ever decide to purchase a non-owner occupied single family property, some lenders allow you to put down as little as 15% for the down payment.

I did a 1031 Exchange for the investment so had a large down payment.

Some of our more active investors use S-Corps, and a few are buying in their own name or with trusts.

Someone to potentially front the down payment or work on some sort of equity deal.