In a typical Solo 401k, the plan can flip (potentially subject to UBIT taxation depending on frequency), hold rentals, lend on mortgages, etc.

What you need to consider is the types and frequency of crimes in the area and how it is changing over time.

Low income + high repair costs + increased frequency of repairs = no thank you.

How many letters you send out and the frequency depends on your budget AS WELL as the ability for you to actually answer the phone and respond to the calls, and your how your area and market responds to the direct mail.best advice. just do it. you won't find out if it works or if it doesn't work if you don't take action and just do it. you'll learn more from one campaign of letters than listening to strangers on the internet lol

A few starting out and possibly get someone to buy the 4bed 2bath for 300k and putting out the frequency to bring a buyer.

You might check out a few of the many blog posts on here or start with one of the books available on the topic like this one: The Book on Tax Strategies for the Savvy Real Estate InvestorProperty tax payment amounts and frequency vary quite a bit by area. 

Look for violent vs non-violent crimes for severity and frequency.

All of them allow you to rent out your condo, they just have restrictions on the frequency and duration, usually 1 rental a year, 30 day min.

Pets will increase the frequency at which carpet needs to be replaced and the extra pet rent can fund that.

Site will only let me add alerts, or modify frequency and manner with which I receive notifications.