Hi Matt,
Wow, I can tell you've been thinking a lot about this! Very good.
With respect to lenders and mortgage brokers: Yes, they can all offer different terms and minimums based on 1) their company's underwriting standards, 2) whether or not they're going to hold the loan or re-sell it, etc. etc. There's some amount of variation, so you just have to keep calling around until you find someone who has a loan product with terms that will work for you.
Regarding other low-down methods: Though not super common, you may be able to find a property, put 10% of your own money down, get the owner to carry 10% of the loan, and then get a "regular" mortgage for the other 80%. Have you already come across this strategy? If not, it's called owner financing, seller financing, seller carry... do a search on the BP forums for it.
Why don't you want a partner? A partner is anyone who is helping you do what you want to do. If you want full control of the property and rights to all of the cash flow and appreciation, take on a partner who is going to loan you the other 10% you need for the 20% down payment, and pay them a fixed rate of return. I've heard of this type of arrangement, and it's usually 6% - 8% a year, interest-only paid monthly, with the principal repaid as a balloon payment in 3-5 years (ie: you refinance and pay them back). You can obviously change any of these details to suit the deal/partnership.
I was resistant to having a partner for a long time, until I learned 2 important things:
1. Would you rather have 50% of something or 100% of nothing?
2. Control of a property and its cash flows is dictated by the operating agreement you have with your partners, not by who puts how much money into the deal.