Before you get too far, I would go talk to every local bank and credit union in the area you want to do this. 

I would appreciate any advice on whether it's a good idea to invest in land on a slope and the potential challenges of building on such terrain.If this seems like a worthwhile investment, can anyone recommend reputable construction companies that specialize in cabin builds on slopes? 

You might want to check with local credit unions or community banks, as they’re often more flexible with second mortgages. 

The one to four is a very comprehensive contract that covers everything and even has room for special provisions when something out of the ordinary needs to be spelled out.When doing not so normal purchases like a sub-to, I dont use the TREC, but one that I created from several other contracts.

So as investing partners it makes sense because we will both have extra cash at the same time, we partner up to cut the risk in half + we both specialize in a couple things the other does not in terms of being a rental property owner (e.g. running the books + marketing vs actually fixing things).  

The property is also on the smaller side and has street parking which is typical for Philly but shows that the property doesn’t have to be anything special.

The downside is they usually come with higher interest rates and shorter loan terms.Partnerships or Co-signers: If your husband or a trusted partner has U.S. legal status and credit history, they might be able to co-sign or help with financing.Cash Purchases: Since you have savings in Canada, you might consider using that for your first property, especially for a smaller rehab project.Foreign National Loans: Some lenders specialize in providing loans for foreign nationals.

I recommend finding an accountant who specializes in real estate taxation and tax planning.You may want to consider working with your accountant remotely to expand your options.I would also recommend looking for a accountant willing to work with you throughout the year.

We have credit scores over 730 and have been "soft approved" for around $750k. 

Promissory notes in general, as they have no collateral, seem a bit higher risk, perhaps mortgage note investing which are backed by residential and sometimes even commercial real estate would be a safer alternative, and yet very lucrative, too,  8-12% yieldsFor extra returns, I put a small portion of my portfolio into BDCs, Business development companies, that specialize in loaning money to growing businesses which are too high risk to get loans from proper banks.