Hi Don't be discouraged, $20k-$30k will definitely allow you to buy, especially given than you are open to location.
If you are planning to owner occupy you can do 5% down with a conventional loan, or 3.5% down with an FHA loan, which gets you anywhere from $400k to over $650k, which leaves you with tons of options. If you are planning to rehab, you should look into the FHA 203k program, which will allow you to also finance the rehab costs, while still only putting 3.5% down, I did one of those myself. There are more hoops to jump through, but it is definitely possible.
I don't like bidding over asking as it doesn't suit my personality, but one thing to know, just because you bid over asking doesn't mean you need extra cash. The loan will still have the same downpayment requirements regardless of the fact that you offered over asking, as long as the property appraises.
There will be plenty of realtors happy to work with you so don't worry about that at all. Some markets may not work for you, but usually the properties that go over asking are the nicest ones, but since you are looking to BRRR you want the less attractive properties anyway, just look for properties that have been on the market for a month or more and you shouldn't have to worry too much about having to over bid.
Keep up your spirits and good luck! Keep researching and learning, you are on the right path.