Should I replace the windows and siding?

[Forrest King]

I have a house (1600 sq ft, 3 bed 1 bath on slab) I paid 105k for. It was a d- in a nice neighborhood, comps in the high 100's and low 200's. In 2008 it appraised for 135k, now worth 146k as is. 

It's a Frankenstein/Goodyear house with old metal siding with a mix of cedar shake and old wood windows from the 50's. 

I got a good estimate to replace 9 windows and 6000sq ft of vinyl siding for just under 20k (I've been quoted 12k-14k for just windows in the past) 

 I'm wondering if this would create enough equity to make it worth it in the short term. I'm planning on a cash out refinance once I'm done rehabbing, then renting it. I have a 20k line of credit against the house currently which I'm using to aquire a 4-plex, and I'm hoping to get another 4plex once I refinance the house. 

 Thank you for your input!