There are specific rules for 1031 exchanges including:The replacement property must be identified within 45 days of transferring the relinquished property.The replacement property must be received within 180 days after the transfer of the relinquished property or the due date of the taxpayer's tax return, whichever is earlier.Special rules apply for exchanges between related parties (defined in § 267(b) or 707(b)(1)).Real property located in the United States and real property located outside the United States are not considered property of like kind.Cost Segregation StudiesA Cost Segregation study is an IRS approved federal income tax tool that increases near term cash flow by utilizing shorter recovery periods for depreciation to accelerate return on investment.

“Genius” me agreed to rent a house for them in exchange for fostering a few of my dogs (I run a dog rescue group.)

Examples of common objections include needing to discuss with a spouse, feeling it's not the right time, uncertainty about the location, or having funds tied up in other investments like a 401K, 1031 exchange, or the stock market.

Would that satisfy 1031 exchange requirements?

General appreciationIf it is in a solid area, maybe the play is appreciation and then a few years later do a 1031 exchange to another, better performing property.With multifamily, typically you can't do STR, but maybe MTR?

@Chandra Faulk,  What you're refering to is what we call a diversification exchange. 

You could also sell some of the houses and do 1031 exchanges into multi tenant properties.

Security deposit amountYou can find plenty of examples by searching for "tenant estoppel certificate doc" or exchanging "doc" with "pdf" for more options.Here is an example and explanation: Sample EstoppelSome have a lot of legal jargon but this document does not need to be so detailed.

Quote from @Olga Daisel: You offered to terminate his agreement early in exchange for three months of rent.

We did a 1031 exchange to roll the money into our dream home.