As long as comps don't reflect those highly upgraded sidings most investors would go with the cheaper option if the purpose is to maximize benefits on the refinance. 16k for siding sounds high if it's a 1000-1500 sqft home

Your suggestion to list on open market likely is the best option for the OP.  

Assuming you go the HELOC route, another option to reduce your costs assuming you have decent credit is to look at credit card balance transfer promotions.Back in 2003-2004 I had HELOCs on my investment properties and interest rates were increasing.

Renters today have more options and properties that are competitively priced to get leased faster!

But I'm looking for the cheapest option to acquire for now and then work my way up to multifamily.

Stessa is a pretty good option but only for the management portion.

Have you considered creative financing options like joint ventures or seller financing to reduce reliance on outside capital?

Quote from @Ashish Acharya: @Cameron Marmon Since you’re married and living in Texas, a community property state, you have the option to treat your 50/50 LLC as a disregarded entity for federal taxes.

I've been at this a while and have over 70% equity in my combined portfolio, and I'm over 50 years of age, so I don't look at creative financing options. 

@Joshua MartinSince you might sell next year, a HELOC is probably the better short-term option—lower upfront costs and flexibility to pay it off when you sell.