I don't have much in the way of recommendations for collateral on other strategies, but if you are interested in Multifamily, I second the recommendation above by @Tony Lin to check out the Old Capital Podcast.

Possibly use the condos as collateral since you don't have the income.

I feel like it is unusual (since it drastically changes their collateral in the deal (by making it less directly accessible in a case of non-payment) and that is in theory what banks want to dissuade, but I've never actually asked one of my lenders about it so I may have been believing a falsehood here. 

The reason banks don't like signing over a loan to an LLC is that they don't have any real collateral against you if the note stops performing.

There is a strategy to fund 100% of the above mentioned items while putting down your 10-20% in a separate collateral account that will be released back to you upon the take out / refinance of the 1st position mortgage.So when you go to refinance this 1st position note and pay it off you'll get your collateral account released back to you.

These typically have low fees and are quick ways to access the cash.A Home Equity Loan typically has higher fees associated with it and is amortized instead of straight-interest (may or may not matter to you).A personal loan may be found to have the highest interest of the three (just a guess) as the bank is collateralizing the loan directly against you and the path to having anything to claim in the event of a default is more cumbersome for them.Could you take more from your 401(k) in terms of a self-funded loan (many providers offer this option and it is a pretty great investment tool)?

Due only to this one provision, lenders won't lend as their collateral in rebuilding is compromised.

You're using your money (equity) as collateral so the bank can sell you new money. 

One thing you should consider is getting a collateral charge mortgage, where there is an increase in your borrowing as you pay down your debt.

I borrowed the money to buy this house from bank using my vehicles as collateral.