However as with most things, this is not exclusively true.

DSCR loans are exclusively for non owner occupied properties. 

Land contracts typically work in a unique fashion where a balloon payment, or lump sum, comes at the end of the repayment period after the repayment plan is negotiated between the two parties.Assumable mortgage: An assumable mortgage is a type of home financing in which buyers are given the opportunity to purchase a home by assuming responsibility for and taking over the seller’s current mortgage (especially if it’s charged at a lower interest rate).Lease purchase: Also known as a rent-to-own contract, a lease purchase agreement speaks to a form of agreement under which renters pay sellers an option fee at an agreed-upon purchase price that gives the renter the exclusive lease option to purchase the property at a later date.Land loans: A land loan is used to facilitate and finance the purchase of a plot of land for later use for residential or business purposes.Holding mortgage: Under a holding mortgage agreement, a homeowner agrees to serve as a lender for the home buyer, and provides a loan for the purchase, which the buyer repays by making monthly payments to the seller.

Is there a reason the two are exclusive options?

UNLESS you mean not exclusively for cash flow...  

You're fine on the 121 exclusion up front. 

There are a handful of states that have 0 capital gains tax, and it seems WA may have some exclusions for RE (confirm with a specialist); however, state level tax is smaller than fed level.

I've Come across a few that initially are seemingly excited and claim to be ready and willing to offer their services in return for me exclusively listing my rehabbed properties with them, as well as passing along clients who's situation may not be suitable for working with an investor (want to sell, but don't NEED to sell).

Look at the "Exclusions" section to see what exclusions there are related to plumbing leaks.

Payments that you make normally fall into one of 3 buckets100% of the payment can be factored in somewhere on the returnPartial payment can be factored somewhere on the return0% of the payment can be factored in somewhere on the returnHouse-hacking also has considerable tax implications in the event that you want to sell this property.You can potentially defer a portion or all of the gain on the investment property with 1031 exclusion.You can potentially exclude a portion or all of the gain on the personal residence with section 121 exclusion.