8 to 10% is tough, especially if you want truly passive income. Real Estate requires some work....
Vanguard has a great REIT index fund that will probably return around ~ 5 to 7% annually including dividends and capital appreciation. You may want to diversify that 500k and put 1/4 of it into a REIT index fund, a 1/4 into a nice utility index fund (both are meant to create and generate passive income with high dividends) another 1/4 in some high quality blue chip stocks like Pepsi, AT&T, Exxon Mobil and Disney - all which pay dividends as well, and lastly put the final 1/4 into a real multi family property that hopefully you can help your Mom manage.
The goal is to live off the income these investments produce and NOT have to use the capital. Hopefully the multi family will appreciate a few % yearly and cash on cash return will be somewhere above 10%
This is by no means any firm financial advice ( I am not an certified financial planner) just some thoughts and opinions based on the very little info you have given.
good luck,
Chris