The property is zoned as a SFR house and likely in a neighborhood of the same.Was the property not appraised by the bank when you got your mortgage?

@Charles Evans, definitely keep all paperwork associated with your tenant (lease, receipts, etc).For expenses that are not split per unit but are for the entire structure (utilities if not separately metered, mortgage interest, etc), keep a record of those payments so your tax pro can deduct a percentage of them for the unit you're renting.

You also need to consider that at a lower percentage of money down you will be paying a Mortgage Insurance Premium or MIP. 

Bitcoin and other cryptocurrency cannot be used as a down payment in a traditional mortgage (Conv, FHA, VA, USDA). 

Hard money loans typically have higher interest rates and shorter repayment terms than traditional mortgages.

Think about a home mortgage--you OWN the property, but the bank might be able to take it away from you.

This means my wife and I could potentially manage up to 20 mortgages together before moving into commercial real estate financing.

If you are buying a buy and hold rental, do not pull a HELOC or you're paying a mortgage payment on the new property AND HELOC interest.

@Jonathan Blanco, I'm and investor and a licensed mortgage broker so I've been on both sides of this conversation.I would look for a lender that (1) listens to you and understands your strategy and needs (hint: it's not always money), (2) has experience working with clients executing your strategy and brings more to the table than just cash - be it advice, relationships, deal-team partners, etc., (3) gives you viable options and explains the pros and cons of each option and (4) you enjoy interacting with - this should be a relationship, not a transaction.Once you find a few lenders like this (and you should have relationships with more than one), then you can start comparing rates and fees.

Becoming a LandlordYour house appreciating at 5% annually = $25K/year.Your parents' larger house = $30K/year.Financing the PlanTake out a mortgage on your house to buy your parents' house.If their mortgage rate is lower than today’s rates (6.75%), keep their mortgage and assume it.Why It WorksYour tenants pay the mortgage—not you.Each monthly payment includes ~$300 toward the principal.