Expensive" is subjective and also a relative term.

You offer to take the property "subject to" the existing bank loan, and ask the seller to loan you some of his $25,000 equity by holding a note for $12,500 called a wrap or an AITD all inclusive trust deed.Then you borrow another $12,500 from a third party who you would give a note secured by a second mortgage on the property as security for the down payment money.

I've been reading about land trusts and it seems that they might be a better vehicle for buying homes that are mortgaged because they may not trigger the due-on-sale clause.If I wanted to buy a house subject to an existing mortgage, could I just make offers to sellers on the MLS or would most selling agents even present a sub2 offer to a seller?

You have to have full documentary income proofs and a subject property with equity in it or that you put equity into in order to borrow.

You put the property under contract for $500 subject to the existing tax lien.

When the Trustee(s) sell Real properties, it is subject to the approval of the court.

Because your subject says "Wholesaling for $256 an hour".

Unpaid taxes are subject to tax sale, either tax certs or tax deeds depending which state.

You sell the property, then take your profit tax free subject to the $250K/$500K cap on the capital gain exclusion.

You aren't searching for comps to your subject as much as you are to see the differences in prices compared to other sales that sold in that time period.