I guess they did not clean the unit for over 3 years and did not call the old property management company when things started to break. 

I have lots of saving in stocks.

When I saw Antoine Martel from FlipSystem Posting Advertisement on social media like this:"You only need $10K ~ $30K to invest in RealEsate doing Flipping and make 100% ROI in 4 months""My clients in FlipSystem averagely spend 4 hours in managing each Flip Project""We help you to quite your JOB in couple of months by doing Flipping""We have few hundreds of success happy client - (Actually there might be few hundreds of clients losing their hard working money)"And lots of other advertisement stating: "Easy, Fast, Low RISK" in their programI thought: "Wow, doing Flipping is so easy and profitable and low-bar to enter in, I should join their program and start make money!"

Apologies, I'm just starting with real estate, however if they're offering a guarantee, isn't that a good thing?

I have a stable and relatively high-paying job with savings and I’m ready to invest.

I've seen 1-2 months rent used in the past, so that might be a good starting point. 

Does anyone have a good source of inventory/ any advice for just getting started?

No current liens but these properties have tax deeds, not warranty deeds if that matters.That as-is value is going to make obtaining financing more difficult for sure.Financing options drop off pretty steeply below a certain dollar amount because foreclosure costs for lenders can be significant.Your best bet may be to connect with some local private lenders (local investor meetups/referrals are a good starting point for this) or local banks.

I had an account on BiggerPockets a decade ago, but starting fresh!

Is it worth it and are there any helpful tips you can share for getting started?